46 



SCIENCE. 



[Vol. XXII. No. 547 



sustain — whether of Darwio, or of Archbishop Ussher — he seeks 

 only to know the truth, whatever may be the consequences. 

 Perhaps the ijoints mentioned in this paper further along have 

 not had suflScient attention hitherto. " Come, let us reason to- 

 gether." 



Tlie first extract above sets the close of the " Ice Age" entirely 

 too far back. One of the objects of this paper is to make good 

 this assertion. From the facts set forth below, it is reasonable to 

 conclude that even on CroH's theory alone the close was not over 

 40,000 years ago, and possibly not over 35,000. If the views of 

 Professor LeConte, given in his paper of January, 1891, have the 

 weight and influence which their importance demands, it seems 

 to me that there need no longer be any contest between gacialists 

 who I'eject the astronomical theory, by reason of the remoteness of 

 the time, and those who refer the ice age to terrestrial causes alone. 

 Professor LeConte's theory is so clearly and tersely set forth that 

 it is best to quote it entire, as given by Professor Wright on 

 pp. 618-9, including the figure used in illustration : — 



PUOCEN; 



" 1. That the continental elevation which commenced in the 

 Pliocene culminated in the early Quaternary, and was, at least, 

 one of the causes of the cold, and therefore of the ice accumula- 

 tion. 



" 2. That the increasing load of ice was the main cause of the 

 subsidence below the present level. 



" 3. That the removal of the ice-load by melting was the cause 

 of the re-elevation to the present condition. 



"4. That all these effects lagged far behind their causes. 



"This lagging of effects behind their causes is seen in all cases 

 where effects are cumulative. For example, the sun's heating 

 power is greatest at midday, but the temperature of the earth and 

 air is greatest two or three hours later; the summer solstice is in 

 June, but the hottest month is July; and in some cases the lagging 

 is much gi-eater. The cause of sea-breezes, — i.e., the heating power 

 of the sun, — culminates at midday, but the effects in producing 

 air-currents culminate late in the afternoon and continue far into 

 the night, long after the reverse cause, i.e., the more rapid cool- 

 ing of the land, has commenced. 



"Now, in the case under consideration, it is probable that the 

 lagging would be enormous in consequence of the reluctant yield- 

 ing of the crust and the capacity of ice to produce the conditions 

 of its own accumulation, Although the elevation produced the 

 cold, and therefore the ice accumulation, yet the latter culminated 

 long after the former had ceased, and even after a contrary move- 

 ment had commenced." 



So far LeConle. 



The close of the glacial epoch as above given — 70,000 years — 

 is wholly arbitrary, and is evidently very far from the truth, as 

 will be shown. At that time the eccentricity of the earth's orbit 

 was nearly twice as great as it is now, and the consequent excess 

 of the sun's time on one side of the equator above that on the 

 other side (depending on the longitude of the perihelion) was 



about fourteen days. It had decreased from thirty-Sve, when 

 the difference was greatest. But this difference of fourteen days 

 would work in the direction of great difference of climate between 

 the hemispheres, and would so continue to work as long as there 

 was any difference at all. And not only so, but the effect would 

 continue and accumulate according to the universal law of nature 

 in the cases above cited, long after the smallest eccentricity had 

 been reached. And that smallest eccentricity occurred less than 

 45,000 years ago, whether the computation be made by the for- 

 mula of LeVerrier or by that of Stockwell. 



The last sentence of the extract from LeConte is significant: 

 " Yet the latter culminated long after the former had ceased and 

 even after a contrary movement had commenced." In this lati- 

 tude the usual temperature for the first week in December is not 

 very different from that of the first week in March. Yet the sun 

 in the first case is more than twenty-two degrees south of the 

 equator, and at the latter date is scarcely five degrees. In like 

 manner, and in accordance with the law above named, suppose 

 the intense cold resulting from the wide glaciation of the northern 

 parts of this continent, to have continued long after the eccen- 

 tricity had reached its minimum, then it is not only possible, but 

 even probable, that the close of the ice age was not more than 

 35,000 years ago, even if 30,000 would not be a more accurate 

 designation. In which event, the objection to the astronomical 

 theory, by reason of the long time elapsed since the days of high 

 eccentricity, is wholly removed. And Professor Wright himself, 

 although long favoring the short period of 10,000 years, has lately 

 seen cause to doubt whether this is not too small. In a letter to 

 the New York Nation, under date of Sept. 15, 1893, in view of his 

 recent investigation of the old northern outlet of the great lakes 

 into the Ottawa River, he says the facts " will . . , considerably 

 lengthen our computation." 



This throwing back of the close of the ice age by the glacialist, 

 and the preceding shortening of the period in accordance with a 

 universal law of nature, may both serve to strengthen the hypoth- 

 esis of LeConte, and commend it to all interested in these ques- 

 tions, as the explanation which best accounts for the admitted 

 facts. 



CURRENT NOTES ON CHEMISTRY.— L 



[Edited by Charles Piatt, Ph.D., F.C.S.) 



Properties of Diamonds. 



The experiments of M. Moissan in the production of artificial 

 diamonds and other precious stones, his remarkable results in the 

 reduction of the most refractory oxides and his whole line of 

 work at high temperatures, are well known to readers of the sci- 

 entific magazines. Some of the more recent investigations have 

 been of the properties of the diamond when heated in oxygen, 

 hydrogen, chlorine, etc. When the temperature is raised slowly 

 the combustion is correspondingly slow and without production 

 of light, being recognized solely by the action of the gas evolved 

 on baryta solution. At 40°-50'' above the point at which this slow 

 combustion takes place the combustion bgcomes more rapid, pro- 

 ducing a visible flame. Yellowish-brown carbonado burned with 

 a flame at 690°; black carbonado with a flame at 710''-720°; 

 transparent Brazilian diamond without a flame at 710°-720°; 

 transparent crystallized Brazilian diamond without a flame at 

 760°-770° ; cut diamond from the Cape without a flame at 

 780°-790°; Brazilian bort and Cape bort without a flame at 790°, 

 and with a flame at 840° ; very hard bort without a flame at 800°, 

 and with a flame at 875°. As a rule, the harder the diamond 

 the higher its point of ignition. 



When heated to 1200° in hydrogen the Cape diamond loses 

 nothing in weight, but becomes lighter in color and less trans- 

 parent; dry chlorine and dry hydrogen fluoride have no action at 

 1100°-1200°. Sulphur attacks diamonds at 1000°, but with car- 

 bonado carbon bisulphide is readily produced at 900". Sodium 

 vapor has no action at 600°. Iron at its melting point attacks 

 the diamond with the production of graphite on cooling; melted 

 platinum also combines readily. Fused potassium hydrogen sul- 

 phate and alkali sulphates, potassium chlorate and nitrate are all 

 without action on the diamond, but, according to Damour, attack 



