June, 1915. 



KNOWLEDGE. 



181 



igneous rock masses in which they occur, and thus give 

 rise to a rock different from that constituting the upper 

 parts. This idea fell into disfavour as an explanation of the 

 differentiation of igneous rocks, but has recently been 

 revived and much strengthened by the description of several 

 igneous rock occurrences in which the heavier minerals 

 are actually concentrated towards the base of the mass. 

 Bowen [American Journal of Science, February, 1915) 

 has placed the matter upon an entirely different footing 

 by actually demonstrating the sinking (and rising) of crystals 

 in artificial melts corresponding in chemical composition 

 to certain igneous rocks. Melts were prepared from which 

 olivine began to crystallise at 1460° C. The temperature 

 was allowed to fall to 1430°, and was maintained at this 

 point for varying periods of time. The melt then consisted 

 of four per cent, olivine crystals and ninety-six per cent. 

 liquid glass. The effects of sinking were plainly visible 

 after fifteen minutes. The small olivine crystals became 

 more and more abundant towards the bottom of the 

 crucible. After eighty minutes the top half of the mass 

 was a clear glass, and all the olivine crystals were collected 

 in a layer one and a half millimetres thick at the base of 

 the crucible. Similar effects were obtained in melts from 

 which pyro.xenes crystallised. On the other hand, crystals 

 of tridymite floated in the melts. The rate of sinking 

 increased with the size and density of the crystals, and 

 decreased as the viscosity of the melt rose. Bowen applies 

 these results to the case of an olivine-rich layer in the 

 diabase sill of the Palisades of the Hudson River, and 

 estimates that in the absence of disturbance by convection 

 currents the accumulation of the olivine crystals might have 

 been accomplished in a period of two hundred to three 

 hundred hours. Bowen concludes that this factor of sinking 

 of crystals in magmas must henceforth be accepted as of 

 fundamental importance in explaining the obser\-ed diversity 

 in certain igneous masses. 



OPHTHALMOSAURUS.— A fine skeleton of this curious 

 reptile has recently been mounted at the Natural History 

 Museum. A note concerning it is contributed to The 

 Geological Magazine for April by Dr. C. W. Andrews. The 

 Ophthalmosaurus is a highly specialised type of Ichthyosaur 

 or Fish-saurian. Its enormous eye-sockets indicate eyes 

 that were suitable for life at considerable depths in the water, 

 and its shape shows adaptation for rapid movement. In 

 fact. Dr. Andrews considers that Ophthalmosaurus holds 

 amongst the reptiles the same place that the swiftly swim- 

 ming toothed whales hold in the Mammalia, and that the 

 similar mode of life in the tv.-o cases has produced somewhat 

 similar modifications in the structure. For example, the 

 front paddles are enlarged, the hind ones reduced in size. 

 There is a large caudal fin ; the head is elongated, with 

 an extremely sharp snout, and with the neck very short. 

 Another peculiarity is the great reduction in the dentition, 

 the adult's teeth being very small and confined to the front 

 of the jaws. The mounted skeleton is thirteen feet six inches 

 in length, of which the head occupies three feet two inches. 



METEOROLOGY. 



By William Marriott, F.R.Met.Soc. 



THE WEATHER OF JUNE.— June, the first of the 

 summer months, is usually characterised from its commence- 

 ment by a considerable increase of temperature. The north- 

 east wind of the spring months now retires before that from 

 the westward. \'egetation proceeds most rapidly towards 

 perfection, and the general appearance of the landscape 

 is the most beautiful of any period of the year. 



June was rather a cold month in the years 1841, 1843, 

 1854, I860, 1869, 1871, 1903, and 1909. It was a very warm 

 month in the years 1846. 1858, 1868, 1877. and 1896. The 

 average mean temperature at Greenwich is 59° -4 : in 1858 

 it was as high as 65° -7, while in 1909 it was as low as 

 53° -9. The average maximum temperature is 70° -7 ; 

 the highest mean was 80° -4 in 1846, and the lowest 64° -6 



in 1903. The average minimum temperature is 49° -9 ; 

 the highest mean was 55° -0 in 1846, and the lowest 46° -0 

 in 1869. The absolute highest temperature recorded was 

 94° -5 on the 16th in 1858, and the absolute lowest 35° -6 

 on the 1st in 1869. The temperature rose to 80° or above on 

 sixteen days in 1846 and on thirteen days in 1858. 



The average rainfall for the month of June is 1 -97-in. ; 

 the greatest amount was 6-07-in. in 1903, and the least 

 0-21 -in. in 1895. The heaviest fall in one day was 1-43-in. 

 on the 12th in 1848. The average number of " rain days " 

 (i.e., on which 0-01-in. fell) is 11-6 ; the greatest number of 

 days was twenty-three in 1860, and the least three in 1887. 

 The average number of thunderstorms is two. 



The average amount of bright sunshine at the Kew 

 Observatory, Richmond, is one hundred and ninety-three 

 hours. 



The average barometric pressure in London for June is 

 29-997-in. ; the highest mean was 30-234-in. in 1826, and 

 the lowest mean was 29-733-in. in 1852. 



AUDIBILITY OF GUN-FIRING IN THE NORTH 

 SEA. — In The Quarterly Journal oi the Royal Meteorological 

 Society for April it is stated that on Sunday, January 24th, 

 several persons in the neighbourhood of Malvern and Here- 

 ford heard what appeared to them to be cannon reports, 

 which they believe to have been the sound of the gun-firing 

 in the naval engagement which was going on at the time 

 in the North Sea. 



Some correspondence also appeared in The Times as to 

 the agitation of pheasants over a considerable part of the 

 country on the same day. Canon Rawnsley, who 

 investigated the matter, said that all his correspondents 

 spoke of the excitement among the pheasants, their fl\-ing 

 high up in the air and " churruking," as quite unhke 

 ordinary excitement in a pheasant preserve on the morning 

 of a battue. He was consequently of the opinion that the 

 birds were really excited by the North Sea battle. Dr. C. 

 Davison suggests that the disturbance might be caused by 

 the sudden swaying of low trees and undergrowth during 

 the passage of the air-waves. 



The weather chart for January 24th shows that the 

 distribution of pressure was favourable for light north- 

 easterly winds with an overcast sky, and so the conditions 

 were such that the sound of the gun-firing in the North Sea 

 may have been heard to a considerable distance in a south- 

 westerly direction. Hereford would be more than two hun- 

 dred miles away. 



ST\TE OF THE ICE IN DANISH WATERS IN 

 FORMER AND PRESENT TIMES.— Mr. C. J. H. Speer- 

 schneider has collected all the information available between 

 the years 690 and I860 tending to throw light upon the 

 question about the ice in Danish waters in former and later 

 times. This has been published in a treatise issued by the 

 Danish Meteorological Institute. From the information 

 collected it appears that the following years had the hardest 

 ice winters : — 



1460 ... 1684 ... 1830 

 1546 ... 1709 ... 1838 



1593 ... 1740 ... 1855 



1608 ... 1776 ... 1871 



1635 ... 1784 ... 1893 



1658 ... 1789 



1670 ... 1799 



The thirteenth to the sixteenth centuries seem to have 

 had from two to three hard ice winters per century. In 

 the seventeenth, eighteenth, and nineteenth centuries 

 there were about five particular ice winters per century. 

 This difference may perhaps be explained by the larger 

 amount of information available for the later years than (or 

 the earlier periods. .\(ter a careful consideration of all the 

 data collected Mr. Spccrschncider is of opinion that there is 

 no reason to believe in any marked difference in the amount 

 of ice in Danish waters during the winters of former periods 

 and of the present day. 



1048 



1269 (?) 



1296 



1306 



1323 



1408 



1423 



