360 



SCIENCE. 



[Vol. I., No. 13. 



and Kettle rivers, in Minnesota, wbere the Kewee- 

 nawan beds are identical in all respects, even to the 

 occurrence of interbedded porphyry -conglomerates 

 and cupriferous amygdaloids, with those of Kewee- 

 naw Point. 



As to the Animikie group, I have only to say, that 

 I have not asserted its identity with the so-called 

 Huronian rocks on the east shore of Lake Supej'inr, 

 spoken of by Mr. Selwyn, but merely its probable 

 identity with the original Huronian of the north 

 shore of Lake Huron, which neither I nor Mr. Sel- 

 wyn have seen, and its certain ideutitj with the iron- 

 bearing schists of tlie south shore of Lake Superior. 

 The term ' Hm-onian' has been so differently used by 

 different members of the Canadian geological corps 

 since the first establisliment of the system, that much 

 doubt must still remain as to whetlier there are two 

 sets of schistose rocks north of Lake Superior, or 

 not. This much, however, I regard as certain; viz., 

 that the flat-lying Animikie rocks of Thunder Bay 

 and northern Minnesota were once continuoiis with 

 seine of the folded schists lying north of them in 

 northern Minnesota and Canada, — the Vermilion 

 Lake iron-bearing schists, for instance, — although 

 now separated from them by belts of gneiss and 

 granite. The lithological differences between the 

 Animikie rocks and the folded schists are-often more 

 apparent than real; while, in many respects, there is 

 a very close lithological lilveness. However, I do not 

 expect, and indeed have no right to expect, acquies- 

 cence in my novel position as to the Animikie rocks 

 until the evidence I have collected has been pub- 

 lished. I am confident, that, with the evidence that 

 I now have, in his hands, Mr. Selwyn would at least 

 think the matter worth looking into. 



With regard to the occurrence of volcanic ash in 

 the Keweenaw series, I must aclinowledge at once, 

 that, so far as field-experience goes, Mr. Selwyn is 

 far better equipped than I to judge of such materials, 

 and that, not having seen Michipicoton Island, I am 

 bound to accept his statement. I understood his first 

 letter to indicate the occurrence of such ash in places 

 which I had myself seen. Nevertheless, I bear in 

 mind that a considerable school of English geologists 

 has been long in the habit of calling almost any de- 

 trit.nl rocks, not distinctly quartzose and associated 

 with eruptive rocks, volcanic ash, when very often, at 

 least, they might be simply derived by water-actioTr 

 from these rocks. Possibly there is some misunder- 

 standing in our use of the term. Most of the detrital: 

 rocks of the Keweenaw series are volcanic detrital 

 matter, in that they have been derived by water- 

 action from the eruptive, massive rocks of the same 

 series; but I used the term as applied to fragniental 

 material produced by the volcanic action itself. I do 

 not know of any /n-oq/' of such an oi'igin in stratified 

 material, other than the vesicular character, and per- 

 haps constant angularity, of the particles, which proof 

 I have failed to find. 



The discussion of such a question as the present 

 one evidently cannot, however, be carried on satis- 

 factorily in the pages of a journal; and I must ask 

 my scientific confreres to defer their judgment until 

 my publications on this subject, now in type, are 

 issued. I?. D. Ikving. 



University of WiBconsin, 

 April 12, 1883. 



Pairing of the first-born. 



As regards the pairing of fce first-born, my calcu- 

 lation of which called forth Mr. Hendricks's criticism, 

 permit me to call attention to the following letter from 

 Mr. Edmands, which I hope will set the matter 



straight. I applied to Mr. Edmands, because mafhe- 

 matics is not my fach ; and I now have the pleasure 

 of thanking him for the very kind attention he has ' 

 given this matter. Chaeles Sedgwick Minot. 



Boston, April 24, 1883. 



As J. E. Hendricks remarks in Science of ApriP 

 13, p. 278, "the chance that the first-born male will 

 pair with the first-born female is as one to ten ; " but 

 Dr. Minot's argument in Science of March 16, p. 

 1G.5, depends upon "the probability of both parents" 

 being first-born, as stated at the beginning of the last 

 paragraph on p. 165. If we first restrict the case to 

 the offspring of first-born males, the chance that both 

 jjarents will be first-born is evidently one in ten. But 

 in the remaining ninety per cent of the race there 

 would be no case of both parents being first-born. 

 Taking the race as a whole, out of one hundred pairs, 

 one pair would be both first-born, nine would have 

 the male only first-born, nine the female only, and 

 eighty-one (9X9) neither male nor female first-born. 

 This does not touch the question whether Dr. Minot 

 is justified in giving no weight to the eigliteen cases 

 i,n a hundred, where only one individual of the pair 

 is first-born. J. Rayner Edmands. 



Cambridge, April 19, 1883. 



Place the ten females in a row, and the ten 

 males opposite them, with the 'first-born' oppo- 

 site each other. The ten males are susceptible of 

 1X2X3X4X5X6X7X8X9X10 permutations, 

 each of which furnishes a distinct system of pairing. 

 Of these, 1X2X3x4X5X6x7X8X9 are possi- 

 ble without disturbing the juxtaposition of the first- 

 born. The chance of their pairing will therefore be, 

 l»x 2x3x4x5x6x7x8x9 _ 

 1X2X3X4X5X6X7X8X9X 10 ~ ^''' 

 as stated by Dr. Hendricks in Science, April 13, 

 p. 278. Mr. Minot's solution is correct only upon 

 the supposition that one iKtir, and no more, will be 

 formed. T. C. M. 



JAMES CLERK MAXWELL. 



Tlie life of James Clerk Maxwell; with a selection 

 from his correspondence and occasional writings, 

 and a sketch of his contributions to science. By 

 Lewis Campbell and William Gaknett. 

 London, Macmillan Sf Co., 1882. 16-1-662 p., 

 3 portr., 4 pi., facsim., etc. 8°. 



James Clerk Maxwell was born iu Edin- 

 burgh on the 13th of June, 1831. He died 

 Nov. 5, 1879. 



The late Professor Benjamin Peirce once 

 said in the hearing of th^ writer, that great 

 geometricians did their best work before they 

 had reached their fortieth year. Tliis can 

 hardly be said of the mathematical physicist ; 

 for the constant accumulation of new facts 

 tends to make mature years the most fruitful 

 in results to the student who still preserves his 

 mental and physical activity. Commoner men 

 doubtless, in time, make good the premature 

 loss to the world of a genius. Those, epochs, 

 however, in a nation's history, in which men of 



