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KRONOS Vol V, No. 2
MEGALITHIC LUNAR OBSERVATORIES – A CRITIQUE (CONCLUDED)
COULD MEGALITHIC MAN HAVE DETERMINED THE LUNAR PERTURBATION?
At no time has Alexander Thom ever discussed whether Megalithic man could actually have measured the very tiny wobble of the Moon. In this section, an attempt will be made to ascertain if such a project would have been viable. The method adopted is as follows:
If we assume, as Thom does, that the motion of the Moon with respect to the Earth has been sensibly constant over the last few thousand years, then a study of the Moon's motion at recent standstill positions should give us a very accurate indication of what Megalithic man would have observed at the standstill positions between three and four thousand years ago.
Figures 1, 2, and 3* show the monthly maximum declination for both northern and southern positions of the Moon over the last three major standstill periods: 1931-1933, 1949-1951, and 1968-1970 respectively. The figures also show the declinations at the two nearest moonsets to the time of the maximum monthly declination for a position of latitude 52° and longitude 0°. The vertical lines therefore indicate the difference in declination between that at the monthly maximum and that at nearest moonsets before and after the monthly maximum. Moonsets were chosen for analysis in preference to moon rises, as the majority of Thom's alignments indicated the former rather than the latter. As moonset times depend on both longitude and latitude, some particular position had to be chosen, although any site in the vicinity of the British Isles would give more or less the same information about these declination differences. The position of latitude 52° and longitude 0° was selected simply because it is the most northerly site in Britain whose moonset times could be directly read off the Ephemeris Tables without the need of time-consuming extrapolation; it is also representative of the area occupied by Thom's lunar sites. For, although in his Megalithic Lunar Observatories Thom generally deals with lunar sites at more northern latitudes, in later articles he contends that Megalithic man also operated observatories at both Stonehenge and Brittany.(44)
An examination of Figures 1, 2, and 3 raises two important questions:
(a) How did Megalithic man manage to obtain the correct maximum monthly declination from observations made when the Moon was setting on an horizon foresight, seeing that the time of the maximum monthly declination would rarely coincide with the time of moonset?
(b) How many moonsets would, on average, be visible and, of these, how many would be suitable for Megalithic man's observation of the lunar perturbation?
I think it is possible to answer these questions. The Declination Deficiencies shown for the last three major standstills would, according to orthodox calculations, be of the same order as those of Megalithic times. Therefore, the extrapolation techniques that Thom claims Megalithic man developed to obtain the maximum monthly declination, from observations made of the nearest setting moons to the time of the maximum monthly declination, should still function efficiently. If it would seem difficult to derive this maximum monthly declination at modern standstill conditions using the methods supplied by Thom, then his arguments would be severely weakened. Similarly, if the length of the lunar day thousands of years ago was very nearly equal to its present length, the Moon would set then, as now, later each day so that the range of times of the relevant moonsets would be representative of those experienced by Megalithic man. We can estimate to some degree the weather conditions prevailing in the Megalithic era, and this should give us some guide as to how many moonsets would have been visible in Megalithic times.
Note that all declinations quoted are corrected for parallax. It is assumed, following Thom, that small changes in declinations will cause linear changes in the observer's position. The maximum monthly declination (MMD) is the maximum declination obtained at each tropical month.
THE EXTRAPOLATION TECHNIQUE
An examination of Figures 1-3 informs us that Megalithic man required techniques to obtain the stake position corresponding to the monthly maximum declination (MMD) from the stake positions obtained by lining up the setting Moon to some horizon foresight. Thom has investigated this problem and his conclusions concerning the extrapolation methods developed by Megalithic man are set out at some length in his Megalithic Lunar Observatories. A brief review of Thom's findings is given below, but the reader should refer to Thom for a more detailed explanation.
At moonsets near the time of the MMD, the observer would stand in such a position so as to have the same part of the setting Moon graze a distinct feature (a notch, perhaps) on the distant horizon. At each moonset he would have to stand in a different position, and these would be marked with a stake. At moonsets before a northern MMD, the stake positions would move south, while after the MMD, the stake positions would move north. If X, Y, and Z were the most extreme southerly stakes they might have been placed in a straight line, as in Figure 4a, or, if the observer had moved out to the side at the same time as he was moving south and then north, they might have been placed as in Figure 4b.
According to Thom, Megalithic man would have realized that the most extreme stake Y would not represent the MMD accurately enough. He would therefore have devised some technique whereby a stake position corresponding to the MMD could have been obtained from the stake positions noted at the nearest moonsets. Thom considers that, at each alignment, a regular series of observations would have revealed a consistent pattern. It would have been found that at each MMD, no matter how stakes X and Z were positioned relative to the most extreme stake Y, the distance from stake Y to the midpoint of stakes X and Z would always be constant. Thom considers that this distance, which he titles "4G", would have been regarded as the characteristic length associated with that particular alignment. Obviously this distance 4G varies with the particular alignment, depending to some extent on the latitude of the site but being mainly contingent on the distance of the notch from the alignment; the farther away the notch the greater 4G would be. This distance 4G is intimately related to a change in declination, which is crucial to Thom's whole megalithic thesis and which will be termed DECLINATION DEFICIENCY.(45)[*!* Image]
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The Declination Deficiency is the change in declination that occurs during the period of a lunar day (approximately 1.0305 days – the time interval between two successive settings or risings) immediately preceding or following the time at which the MMD occurred. The fall in declination on both sides of the MMD is symmetrical. A particular case is when moonset occurs at the time of the MMD. Then the Declination Deficiency is simply the difference in declination between that at the moonset, that was simultaneous with the MMD, and the declination at either moonset before or after it.
In this case, both stakes X and Z would be exactly the same distance away from stake Y. (If the stakes had been laid out in a straight line, X and Z would coincide.) It can easily be seen that the distance between stake Y and either X or Z (the distance 4G) is equal to the distance on the ground covered by the observer during the change in declination equal to the Declination Deficiency. From this particular case, we can see the important general relationship between the distance 4G, which can be found by measurement on the ground, and the all important declination change – the Declination Deficiency.
Megalithic man was now supposedly able to proceed with the first step in his extrapolation procedure for, according to Thom, he had extensive knowledge of the field geometry pertaining to arcs, chords, and sagittas. If his stakes were positioned, as in Figure 4b, he would simply have measured a length G from the midpoint of the two most extreme stakes Y and Z (see Figure 5). This step would have given him a reasonable guide to the stake position corresponding to the MMD, provided the distance between stakes Y and Z, which we shall call 2P, was quite small. Megalithic man would also have discovered that this distance, 2P, would vary between zero and 4G. When the distance was 4G, the most extreme stake Y would actually represent the MMD.
When 2P started to increase, an appreciable error in the extrapolated position would occur, and this could only be corrected by the application of much more sophisticated methods. In Thom's view, Megalithic man was equal to the demands incurred and his efforts "must be regarded as one of man's greatest achievements". How he could have done so is set down below.
In Figure 5, [h] is the distance required to give the true stake position for the MMD. This distance was obtained from geometrical models involving the lengths 4G and P so that h = P2/4G. Hence, h could be obtained either from a triangular method (Fig. 6a) where the lengths 4G or sometimes G are laid out on the ground as at Temple Wood (Fig. 7a), or else from a sector method (Fig. 6b) where stones are laid out in a geometrical grid formation in the shape of a fan as at Mid Clyth (Fig. 7b). This sector method has two advantages for, in addition to obtaining the distance n, a distance Y, can also be obtained which, when added to the extreme stake position, gives the correct stake position for the MMD. This distance Y1 = m2/4G, where m = 2G – P, is derived from the sector model using m the same way that h is found from P. The second advantage of using the sector method is that when using either h or Y1 the size of the grid needed is halved. To quote Thom: "When P is less than G use h = P2/4G, and when P is greater than G use Y1 = m2/4G. This explains why the main sector at Mid Clyth has a base and a height of exactly G."[*!* Image] Fig 7a TEMPLE WOOD
Fig 7b MID CLYTH
Formidable objections have been offered against Thom's belief that Megalithic man was capable of employing ingenious extrapolation techniques. As mentioned previously, this belief is much at odds with orthodox opinion. In fact, one of the few archaeologists who is sympathetic to Thom's work, Professor Atkinson, has expressed strong reservations about the ability of Megalithic man to develop and use these techniques. More particular objections have been raised against the extrapolation distances and stone grids that Thom has found on the ground. It has been pointed out that it would not be difficult to find, near a lunar site, two seemingly significant features whose distance apart would correspond to an extrapolation length. Critical attention has also been focused on the stone sectors, for there are only four of these and many stones are missing. Thom has fitted the remaining stones into a regular array, employing his megalithic yard as the grid parameter. The statistical techniques he has used to justify these patterns have been questioned by other statisticians.
But my concern here is not with the above aspects of the controversy; it is rather with what I shall call the technological difficulties confronting Megalithic man – i.e., the feasibility of his actually being able to perform these extrapolation techniques on the ground to the degree of accuracy that Thom's thesis demands. And it is precisely here that fundamental objections can be raised against the underlying philosophy of Thom's Megalithic Lunar Observatories.
Thom used a value for the Declination Deficiency of 49.3', which he regarded as immutable; thus, the characteristic distance 4G for each lunar line was also considered constant. Thom, however, made a grievous error, for an examination of an Ephemeris Table would surely have convinced him that the Declination Deficiency is not constant but is variable within wide limits. This point was emphasized by Dr. D. C. Heggie(46) who also noted that the mean Declination Deficiency is about 10% higher than Thom's figure. I have, accordingly, calculated the Declination Deficiencies at each MMD, for both northern and southern values, over the last three major standstills.
These Declination Deficiencies have been obtained by using a method similar to that used for obtaining the characteristic distance 4G from moonset stake positions. These Declination Deficiencies were checked against sample ones obtained directly from the Ephemeris Tables and were found to agree to within a minute (1'). Declination Deficiencies read directly from the tables, by consideration of the length of the lunar day, are difficult to obtain accurately as the lunar day tends to vary about its mean value of 1.0305 solar days. A sample calculation of a Declination Deficiency is given below.
Suppose the moonsets nearest the MMD were at 03 50, 04 40, and 05 30 hrs and the corresponding declinations were 27° 50', 28° 32', and 27° 10' respectively. Then the "midpoint" of 27° 50' and 27° 10' would be 27° 30' and the Declination Deficiency would therefore be 28° 32' – 27° 30' = 62'.
These values for the Declination Deficiency over the last three major standstills are plotted in Fig. 8 and are also given in Tables 1A – 1F. The reader will notice the wide fluctuations in the Declination Deficiencies at the major standstills. There are two periodic variations, one long term, the other short term, which are a consequence of the complicated motion of the lunar orbit.
The position of the lunar perigee is not fixed relative to the stars but has a direct motion of 401" per day. Relative to the first point of Aries, a complete revolution occurs in about eight years and 310 days. The period of the major standstill is 18.61 years so the interaction action of these two times produces an approximate 186-year periodicity in the range of Declination Deficiency values at the major standstills. Over the time scale shown in Fig. 8, the northern or positive Declination Deficiencies reached their maximum values at the 1969 standstill while those of the southern were at a minimum; before this, the northern values tended towards their maximum at the 1876 standstill while the southern values were then at a minimum.[*!* Image] Figure 8. DECLINATION DEFICIENCY AT LAST THREE MAJOR STANDSTILLS.
Both the rate of motion of the perigee and the value of the eccentricity are variable, their variations being connected and having the same period, viz., half the time between two consecutive passages of the Sun through the perigee. The latter period is 412 days, so that the period of the variation of the eccentricity is 206 days, which accounts for the short term fluctuations.
Even if the constancy of the lunar orbit is assumed for the last five thousand years, Megalithic man would still have had to struggle with these fluctuations. Thom considers that they studied the perturbation over at least a period of 100 years. So, undoubtedly, they too would have noticed that the so-called characteristic distance 4G would have varied within wide limits. This, however, seems much at variance with Thom's views on the subject and accordingly, two objections must be raised against Thom's methodology:
Firstly, Thom claims to have discovered evidence of extrapolation lengths, equivalent to either 4G or G, permanently set out on the ground at certain of his lunar sites. These lengths, along with the corresponding Declination Deficiencies, are presented for each site in Table 2. As seen, these Declination Deficiencies range from 33' to 54'. If the actual Declination Deficiency could have been as high as 71', as has happened at the last two standstills, then there would have been vast errors in using these fixed 4G values. The differences at some sites would have been of the order of 100%, or about 36' of Declination Deficiency. A quarter of this value, equivalent to the crucial G length, is 9' which is exactly the amplitude of the perturbation.
Secondly, Thom's extrapolation thesis depends on Megalithic man's ability to detect the constant characteristic distance 4G. However, as shown above, the Declination Deficiencies upon which these 4G values depend change rapidly. Therefore, the distance on the ground between the most extreme stake and the midpoint of the two adjacent stakes would also vary considerably. So how could Megalithic man have determined a fixed 4G value, as Thom has stated? In reply, it could be argued that Megalithic man was aware of the fluctuations in his 4G distances and would recalculate a new 4G value for each MMD. But in that case he would not have established permanent 4G or G values on the ground and certainly not have laid out the stone sectors.
One further point concerning the stone sectors can also be made: Thom stresses that the scale of the grid can be reduced by half, as at Mid Clyth, resulting in great savings of time, manpower, and stones while, at the same time, showing the cleverness of Megalithic man. However, it can be seen from Figures 9a and 9b that an even smaller grid could have been used to give the same results. If Megalithic man was as capable and economically minded as Thom contends, it seems strange that he did not devise this smaller grid.[*!* Image]
VISIBILITY IN THE MEGALITHIC PERIOD
One of the main obstacles to the acceptance of Thom's lunar hypothesis is that Megalithic man required much better observing conditions, at least in Scotland, than those prevailing today. Some
of Thom's supporters(47) have implied that his thesis depends upon there having been a significantly superior weather regime in the past. In order to arrive at reliable observing conditions in the Megalithic era it is necessary to examine the suitability of present conditions for astronomical observations. Writing of the British Isles as a whole, Manley stated:
At Leuchars, on the east coast of Scotland, the frequency with which a single cloud layer was observed covering at least 5/8ths of the sky between 1960 and 1969 was 66.7%.(49) Working south of Glasgow, Livesey analyzed the incidence of cloud cover between 1960 and 1976 with the results shown in Table 3a, b, and c.(50) We may therefore conclude that, at present, the odds are about 2:1 against any given astronomical event being observable in Scotland and, if the effects of haze and fog are allowed for, the odds against observation of horizon events will be greater still.
In the past, the absence of industrial and large-scale domestic pollution would have markedly reduced the effect of haze. But such pollution makes no significant contribution to the statistics for the cloud cover quoted above. However, it has been stated that the climatic period known as the "sub-Boreal" (c.3000 – c.800 B.C.) was warmer, drier, and presumably less cloudy than today.
There is general agreement that between 3000 B.C. and 1500 B.C. summers were warmer than at present. Lamb(51) would have winters also warmer down to c.2000 B.C., though Iversen(52) has found evidence for generally colder winters. Lamb(53) quotes evidence of dry conditions but elsewhere argues for a rainfall slightly higher than the average for 1900-1950 A.D.(54) He also rejects Brooks' view "that rainfall between 3000 and 2000 B.C. was as little as 42%-52% of that of the present".(55)
Lamb(56) has calculated the distribution of atmospheric pressure at sea level for various dates and deduces that the frequency of anticyclones blocking the passage of depressions across the British Isles was greater c.2000 B.C. than at any time since. This would be consistent with warm summers, with a "continental" rainfall maximum in summer, and with relatively cold dry winters. Rainfall would have occurred in shorter, heavier falls and with less protracted drizzle than at present. This is the climatic regime on the basis of which Thom's supporters argue that viewing conditions were significantly better than they are today. But no one has attempted to show how this weather pattern would have affected observing conditions.
It is not claimed that the degree of difference between the sub-Boreal climate and that of the present was great. Rainfall may have been similar, though differently distributed; mean temperatures may have been up to 2° C higher.
The blocking of depressions would reduce the incidence of southwest winds and the passage of fronts with their associated belts of clouds and rain. If areas of high pressure developed to the west of the Hebrides, clear weather could be expected, though the north of Scotland might experience cloudy conditions associated with the passage of depressions further north. "Highs" developing to the northeast, and giving rise to easterly winds, might produce clear skies, but could also develop extensive cloud cover, especially in winter. South winds on the westerly flanks of anti-cyclones might also produce extensive cloud cover.(57) The presence of areas of high pressure blocking the passage of depressions cannot, therefore, be equated with clear skies, especially in winter. Moreover, in summer, easterly winds and clear skies are often associated with haze, and even without the aggravation of pollution this must have rendered observations of the Moon on the horizon difficult. In general, then, summer weather during much of the sub-Boreal may have been less cloudy, though frequently hazy, but winters may often have been dull and overcast.
Lamb(58) has suggested that, because of the increased influence of blocking "highs" whose formation and duration are unpredictable, the range of annual variation in weather would have been greater than at present. This means that even if most years were relatively favorable for observations, these would have been interrupted during the periodic bad years.
There is also substantial evidence of wetter and colder phases within the period. Lamb(59) quotes periods of peat-bog formation. In Ireland these are dated to 2800, 2400, 2200, 2000, and 1500 B.C.; in Scandinavia to 2800 and 2200 B.C. – though climatic deterioration is not the only possible cause of this. Manley(60) quotes advances of Alpine glaciers at about 2650 and 1750 B.C. Wiseman(61) quotes cooler temperatures in the equatorial Atlantic at about 2800, 2350, and 1850 B.C. and correlates them with advances of Alaskan glaciers and the growth of English peat-bogs. Frenzel(62) summarizes evidence pointing to cool, moist phases at about 2200-1850 and 1700-1400 B.C. There are difficulties in interpreting all this, but the evidence tends to agree that considerable fluctuations of temperature and precipitation occurred during the sub-Boreal period.
Climate also affects observing conditions indirectly through its influence on vegetation. An increase in the extent of natural woodland would have reduced opportunities for observing the horizon. Lamb(63) quotes evidence of much more widespread forest cover in the 4th millennium B.C. and Manley(64) suggests that, in Scotland, the greatest extension of woodland may have taken place during the sub-Boreal. Many of today's exposed moorlands may have then been wooded and, since human agriculture and stock-breeding made little impact in Scotland till the early Middle Ages, most present-day arable and pasture land must also have been forested (though the chalk uplands of southern England appear to have been forest-free). Thus many alignments which can be seen today must have been obscured in the age of the megaliths.
Thus the overall picture is one of long periods during which the weather was more favorable, but perhaps not significantly so, than today. This, however, was interrupted by phases when conditions were no better than at present. To have left any record at all, these cool moist phases must have lasted long enough to have disrupted the observations of an illiterate society whose members had a much shorter life expectancy than at present. Under such variable skies natural woodland flourished which covered much present-day moor and farm-land, obscuring many potential alignments and perhaps diverting man's attention away from the horizon altogether.
WERE ENOUGH MOONSETS AVAILABLE FOR MEASURING THE PERTURBATION?
It has been shown that Thom's distance 4G is not constant but varies over wide limits. These long and short term fluctuations preclude the use of a constant 4G value for extrapolating the stake position corresponding to the MMD. Megalithic man, in order to establish accurate stake positions for the MMD, must therefore have made observations of the three moonsets nearest in time to the MMD. Disregarding weather conditions for the moment, consider the following:
(a) The period from new moon to new moon is called the synodical month which averages 29.53 days. The mean interval between declination maxima, the MMD, is not the draconic month as Thom states, but the tropical month of 27.32 days. Therefore, the full
moon will rarely coincide with the MMD. Tables 1A-1F show, among other things, the age or phase of the Moon at each MMD, and it can be seen from these tables that the full moon only coincides with the MMD about every thirteenth tropical month, or about once a year. Megalithic man could not have relied solely on the full moon for his observations. One other factor is that the Moon sets progressively later each day on account of the mean lunar day being 1.0305 days and this, in conjunction with the period of the tropical month, gives rise to an important condition.
As can be seen from Tables 1A-1F, the incommensurability of these two times produces an effect such that the mean times of the three moonsets nearest to the MMD decrease slowly with successive MMDs. Comparing this "ordered regression" of these important moonset times with the data supplied in Table 4 leads us to the conclusion that, over the last three standstills, one or more of the moonsets nearest to the MMD occurred during daytime conditions every other six-month period. During these times, when the Moon set in an astronomically bright sky, a sequence of observations on three successive nights would have been impossible.
Over every other interval of six months, the nearest moonsets to the MMDs would occur under night conditions and can be assumed to be theoretically visible. Megalithic man would have "enjoyed" similar conditions and one wonders whether it would have been possible to determine the extent of the perturbation from the observations made during these six-month periods.
(b) The apparent shape of the Moon to an observer on Earth consists of a semi-circle and a semi-ellipse – the semi-circle portion being the boundary facing the Sun. At full moon the semi-ellipse becomes a semi-circle and at half moon a straight line. The common diameter of the semi-circle and this semi-ellipse, which is the line joining the cusps of the Moon, is perpendicular to the plane passing through the observer and the centers of the Sun and Moon. The angle between this plane and the observer's horizon is very variable, so that for a given "age" of the Moon, the line joining the cusps will be at different angles to the horizon in different months, sometimes being nearly vertical, at other times nearly horizontal. This suggests that the lower limb of the Moon (by altitude) could have been more frequently observed than the upper limb (by altitude). Therefore, lines said to indicate declinations ± (e ± i ± D + S) and - (e ± i ± D + S) could not have utilized certain of the rising or setting Moons even though they may have been visible on the horizon.
(c) It would be very difficult to observe the very fine crescent Moon on the horizon (1) because of its proximity to the Sun, (2) because of the reduced brightness of the crescent Moon, and (3) because of the general difficulty in seeing astronomical bodies on the horizon. This again would reduce the number of moonsets available for observation.
To sum up, over every other six-month period, the moonsets nearest to the time of the MMDs would be invisible. In the other six-month periods, for reasons given above in (b) and (c), not all moonsets would be suitable for the type of observations that Megalithic man would have demanded. And when weather conditions are taken into account, the number of useful moonsets must be reduced even further. At present, in Scotland, only about one third of the nights are clear and the chances of obtaining three clear nights in a row are much less than one in twenty using the figures in Table 3a, b, and c.
It is difficult to imagine that these figures would be much improved over Megalithic times as a whole if the information regarding the weather regime, as it was then, is taken into account. There could well have been an increase in the number of nights propitious for astronomical observation, but the order of this increase would, on the evidence presented previously, have had only a peripheral effect. The sole conclusion that can be drawn is that Megalithic man would have faced insuperable difficulties in attempting to measure the lunar perturbation by the methods that Thom suggests.
It has been shown that Professor Alexander Thom's hypothesis, that Megalithic man made a serious study of the lunar perturbation, is based on nebulous foundations.
In the first part of this article (see KRONOS V:1, pp. 47-63), Thom's methodology with regard to his selection and assessment of lunar lines, his assignment of a definite declination to the lines, and the dating methods he uses to show the homogeneity of the lines, was shown to be both inconsistent and unreliable.
In the second section, the feasibility of Megalithic man's actually accomplishing a project as difficult as determining the perturbation was investigated by assuming, as Thom does, the fundamental constancy of the Moon's motions over the last five thousand years. It seems evident that Megalithic man would have encountered two seemingly insurmountable obstacles in his supposed study of the wobble.
Firstly, the extrapolation techniques required to establish the Maximum Monthly Declination, from declinations obtained from observation of the setting Moon on an horizon foresight, would not have worked satisfactorily due to both the short and the long range fluctuations in the Declination Deficiency. This is a consequence of the extrapolation lengths which Thom claims to have discovered permanently set out at various lunar sites, and which are so crucial to the vindication of his argument, since the lengths have a necessarily constant value. Two possibilities exist here for, if they were used in the manner Thom indicates, they would by their invariance have produced wildly erroneous results. Alternatively, no permanent record of the extrapolation lengths existed, for Megalithic man was aware of the rapid changes in these lengths, and he would have continuously remeasured these lengths for each MMD. Obviously Thom's thesis is much reduced in value if these "permanent extrapolation lengths" can no longer be regarded as strong evidence for the veracity of his case.
Secondly, Megalithic man required observations on the horizon of the three setting Moons nearest in time to the MMD. We found, however, that observations over every other six-month period would have been impossible due to the relevant moonsets occurring under daytime conditions. In the other six-month periods, for a variety of reasons, a significant number of moonsets would not have been suitable for the type of observation that Megalithic man would have required. The weight of this evidence would seem to make untenable the claim that Megalithic man studied the wobble.
To conclude, we may quote Jon Patrick:
And this seems to be the raison d'être of Thom's Megalithic Lunar Observatories.
REFERENCES44. Journal for the History of Astronomy, 7 (1976), pp. 147-160; Ibid., pp. 11-26; Ibid., 5 (1974), pp. 71-90; Ibid., 6 (1975), pp. 19-29.
45. See MLO, pp. 85-87 for a more detailed description.
46. Antiquity, 46 (1972), p. 47.
47. J. E. Wood, Sun, Moon and Standing Stones (Oxford, 1978), p. 182.
48. Manley, Climate and the British Scene (1952), p. 133.
49. Information received from the Scottish Meteorological Office, 1978.
50. R. J. Livesey, Journal of the British Astronomical Association, (1971), p. 292; also private communication.
51. H. H. Lamb, R. P. Lewis, and A. Woodroffe, World Climate from 8000 B.C. – 0 B.C., as edited by Sawyer (1969) – Proceedings of the Overseen, Symposium held at Imperial College (London, 18-19 April, 1966).
52. J. Iversen, "Viscum, Hedera and Ilex as Climate Indicators," Geol. För Forhandl, Stockholm, 66 (1944), p. 463.
53. H. H. Lamb, Philosophical Transactions of the Royal Society of London, 276, No. 1275, pp. 211, 212
54. Idem, in Sawyer (see note No. 51), pp. 190-193.
55. C. E. P. Brooks, Quart. J. R. Met. Soc., 60 (1934), pp. 377-395.
56. H. H. Lamb, in Sawyer (see note No. 51), pp. 174-211.
57. Manley, op. cit., Chapter 4.
58. H. H. Lamb, Phil. Trans., op. cit . (see note No.53), p. 218.
59. Ibid., p. 223.
60. Manley, in Sawyer (see note No. 51), p. 31.
61. Wiseman, in Ibid., p. 93.
62. Frenzel, in Ibid., p. 108.
63. H. H. Lamb, in Ibid., p. 209.
64. Manley, in Ibid., p. 34.
65. Irish Arch. Res. Forum II, 2 (1975), p. 9.
[*!* Image]. TABLE 1A MAJOR STANDSTILLS 1931-1933 NORTHERN
[*!* Image] TABLE 2 - PERMANENT 4G and G VALUES with CORRESPONDING DECLINATION DEFICIENCIES
TABLE 3 (a) The percentage of nights per month when observation was impossible due to cloud between 1960 and 1976.
TABLE 3 (b) Nights when observations were possible came in groups of one, two or more consecutive nights, and the distribution is as follows.
TABLE 3 (c) Likewise cloudy nights came in series of one or more consecutive nights and their distribution was as follows.
TABLE 4 SUNRISE AND SUNSET TIMES and also ASTRONOMICAL TWIGHLIGHT AT 52° 0°
Information taken from J. Brit. Astro. Ass. 1971 81 4 P-292 and also in private communication from Mr. R.J. Livesy.