608 
NATURE 
[ Oct. 21, 1886 
If we make e = 23° 27’ we find that the heat received during 
the summer (equinox to equinox) of each hemisphere is 627 £, 
while the heat during the winter of each hemisphere is 373 £. 
More briefly still. If each hemisphere receives in the year a 
quantity of sun-heat represented by 365 units, then 229 of these 
are during summer, and 136 during winter. These figures are 
independent of the eccentricity of the earth’s orbit. 
The length of the summer is defined to be the interval when 
the sun’s centre is above the equator. The length will of course 
vary with the eccentricity and with the position of the equinoxes 
on the orbit. We need only take the extreme case where the 
line of equinoxes is perpendicular to the major axis of the orbit. 
The maximum difference between the length of summer and of 
winter is thus 
365 days x eccentricity. 
I take the maximum eccentricity of the earth’s orbit to be 
0°0745, 
this being the mean of the values by Leverrier, Lagrange, and 
Stockwell (see Croll, ‘‘ Climate and Temp.,” p. 531), and, 
therefore, the greatest difference between summer and winter 
will be about 33 days, z.e. one season is 199 days, and the other 
is 166 days. 
The total quantity of heat received during the year on each 
hemisphere is practically independent of the eccentricity ; but 
the mode in which that heat is received at the different seasons 
will vary, and thus give rise to the following extreme cases :— 
GLACIAL 
(Summer) 229 heat units spread over 166 days. 
(Winter) 136 » » 199 5, 
INTERGLACIAL 
(Summer) 229 heat units spread over 199 days. 
(Winter) 136 166 ,, 
We hence deduce the following, where unity represents the 
mean daily heat for the whole year on one hemisphere :— 
” ” 
GLACIAL 
Mean daily sun-heat in summer (short) ... 1°38 
9 3 winter (long) vee BOS 
INTERGLACIAL 
Mean daily sun-heat in summer (long) 1°16 
50 0 winter (short) “SI 
PRESENT (NORTHERN HEMISPHERE) 
Mean daily sun-heat in summer (186 days) 1°24 
op 8 winter (179 days)... 0775 
These figures exhibit a thermal force of great intensity. The 
unit represents all the mean daily heat received from the sun by 
which the earth is warmed up from the temperature of space. 
The heat unit in fact maintains a temperature perhaps 300°, or 
even more, above what the earth would have without that heat. 
Each tenth of a unit may thus roughly be said to correspond to 
a rise or fall of mean temperature of 30° or more. The long 
winter of 199 days, when the average heat is only two-thirds of 
a unit, leads to the accumulation of ice and snow, which form 
the Glacial epoch. The short winter of 166 days, where the 
temperature is ‘06 of a unit above that of our present winter, 
presents the condition necessary for the mild interglacial epoch. 
THE BRITISH ASSOCIATION 
SECTION H—AnTHROPOLOGY 
The Native Tribes of the Egyptian Siidan, by Sir Charles 
Wilson, K.C.B.—These may be divided into four distinct 
groups—the Hamitic, Semitic, Nuba, and Negro ; but the first 
three only were dealt with in this paper. The largest tribe in 
the Sudan is the Kabbabish. They extend from Dongola to the 
confines of Darfiir; they speak a pure Koranic Arabic, and 
have a tradition that they came from Tunis ; they are possibly 
of Berber descent, but the Sheikhs are apparently of Arab 
origin. They are divided into two great branches and several 
minor clans, One clan, Kawahleh, appears to be of Arab 
origin. 
Lhe Celtic and Germanic Designs on Runic Crosses, by Prof. 
W. Boyd Dawkins.—The author said that although it is gene- 
rally assumed by archeologists that the early Irish manuscripts, 
such as the illuminated Gospels of St. Cuthbert and St. Chad, 
are of pure Irish art, and that consequently the interlacing 
“‘rope-” or ‘‘basket-work”, pattern is distinctly Trish and 
Celtic, such an assumption is not warranted by experience. A 
consideration of the distribution of the designs on ornaments and 
monuments in the British Isles and in France, Scandinavia, and 
Germany, lead to the conclusion that the art was probably 
derived from the centres of civilisation in South Europe, princi- 
pally Greek and Etruscan, and it has clearly been proved by 
Chantre to have been introduced into France from Italy. The 
square interlacing pattern does not occur in France or the 
British Isles in association with any remains of a date anterior to 
the movement of the Germanic tribes against the Roman Em- 
pire, and as it is only found in regions into which the German 
tribes penetrated, it may be concluded that it is distinctly Ger- 
manic, and not Celtic, still less ‘‘ pure Irish.” 
The Scientific Prevention of Consumption, by G. W. 
Hambleton.—There are two distinct objects to be accom- 
plished in the prevention of consumption. On the one hand we 
have to secure an adequate amount of breathing capacity in 
proportion to the rest of the body, and on the other to prevent 
either compression of the chest or injury to the lungs. This can 
be done by adopting those measures that tend to the develop- 
ment of the breathing capacity, and suppressing or obviating those 
conditions that compress or injure the lungs. By adopting 
measures is meant placing men, women, and children under 
conditions of habitation, clothing, education, and urging upon 
them habits that tend individually and collectively to develop 
the lungs. 
Dragon Sacrifices at the Vernal Equinox, by George St. 
Clair, F.G.S.—The object of this paper was to show that human 
sacrifice, which prevailed extensively in early times, was a 
custom connected especially with the vernal equinox, and that 
the offerings were made to appease a mythical dragon which 
made its demand at that time. The dragon of mythology was 
identified and defined, and it was shown in what sense he opened 
his jaws at the spring season of the year. Human sacrifice was 
practised more especially at the spring of the year, or (in other 
instances) in honour of deities who once presided over equinox 
constellations, Artemis and Cronus, to whom. this homage 
was chiefly shown, were both connected with the zodiacal sign 
Scorpio, and, according to M. Ernest de Bunsen, Scorpio was 
the starting-point of the primitive calendar. If the festival of 
Saturn did not get displaced or misplaced through the precession 
movement, it was still a festival in honour of the god of the 
under-world, and that meant death and the grave. Tradition 
says that human sacrifices were abolished by Hercules. As 
Scorpio rises with Hercules, and ceases to be a dark sign, the 
mythology is consistent with itself, 
Evidence of Pre-Glacial Man in North Wales, by Dr. Henry 
Hicks, F.R.S.— The author in this paper described the 
conditions under which a number of flint instruments were 
discovered during the researches carried on by Mr. E. B. Lux- 
more and himself in the Ffynnon Beuno and Cae Gwyn Caves, 
in the Vale of Clwydd, in the years 1884-86. Last year a 
grant was made by the British Association for the purpose of 
carrying on the explorations, chiefly with the object of obtaining 
further evidence as to the age of the deposits in the caverns, 
The results obtained this year are highly confirmatory of the 
views which he (Dr. Hicks) had previously held, and have a 
very important bearing on the antiquity of man in Britain. It 
was found that the main entrance to the Cae Gwyn Cave had 
been blocked up by a considerable thickness of Glacial beds, 
which must have been deposited subsequently to the occupation 
of the cave by the Pleistocene mammals. A shaft was dug 
through these beds in front of the entrance to a depth of over 
20 feet, and in the bone-earth, which extended outwards under 
the Glacial beds on the south side of the entrance, a small well- 
worked flint flake was discovered. Its position being ahout 18 
inches beneath the lowest bed of sand, it seemed to be clear 
that the contents of the cavern must have been washed out by 
marine action during the great submergence in mid-Glacial times, 
and then covered by marine sand and an upper covering of boul- 
der-clay. He believed that the flint implements, lance-heads, and 
scrapers found in the caverns were also of the same age as this 
flint flake, and hence that they must have been the work of 
pre-Glacial man. 
The Recent Exploration of Gop Cairn and Cave, by Prof. 
Boyd Dawkins.—This was a paper on the exploration of Gop 
Cairn and Cave, near Gop Hall, New Market, St. Asaph, 
now being carried on by Mr. Pochin, Mr. P. G. Pochin, 
