492 



NA TURE 



[February 24, 1910 



polonium is radium D (radio-lead), which grows 

 polonium and has a period of half-transformation of 

 about twent}' years. Since polonium breaks up about 

 5000 times faster than radium, its activity, weight for 

 weight, should be about 5000 times greater than that 

 of radium. There is nothing surprising in this, for the 

 radium emanation has an activity about 200,000 times 

 that of radium, while radium A (period three minutes) 

 must have an activity 400 million times that of radium 

 itself. Since the radiation from polonium is entirely in 

 the form of a rays, it is to be expected that the radia- 

 tion from it would show chemical and physical effects 

 identical with those observed for pure emanation, the 

 only difference being that the products of the latter 

 emit 6 and 7 rays as well. 



Apart from the interest of obtaining a weighable 

 quantity of polonium in a pure state, the real import- 

 ance of the present investigations of Mme. Curie lies 

 in the probable solution of the question of the nature 

 of the substance into which the polonium is trans- 

 formed. This problem lias been much discussed ip 

 recent years. Since polonium emits a particles, one 

 of its products of decomposition, as for all the other 

 a-ray products, should be helium. The production of 

 helium from a preparation of polonium has been 

 observed by Rutherford and Boltwood (Manchester 

 Lit. and Phil. Society, November 30, 1909), and also 

 by Mme. Curie and Debierne in their present experi- 

 ments. Boltwood several j-ears ago suggested that the 

 end product of the radium series was lead, and has 

 collected strong evidence in support of this view by 

 comparing the amount of helium and lead in old radio- 

 active minerals. Since polonium is the last of the 

 active products observed in the radium series, it is to 

 be expected that polonium should be transformed into 

 helium and lead, one atom of polonium producing one 

 atom of helium and one atom of lead. This point of 

 view receives additional w-eight from consideration of 

 the atomic weight to be expected for the end product 

 of radium. Since in the uranium-radium series, seven 

 a particles, each of which is an atom of helium of 

 atomic weight four, are successively expelled before 

 radium F is reached, the atomic weight of polonium 

 should be 7x4 = 28 units less than uranium (atomic 

 weight 238's). This gives an atomic weight of 

 polonium of 2io'5, and after the loss of an a particle, 

 .•I final product of atomic weight 2o6'5 — a value very 

 close to the atomic weight of lead. 



It is a matter of very great interest and importance 

 to settle definitely whether polonium changes into 

 lead. The evidence as a whole has long been in 

 favour of that supposition. The outlook is verv pro- 

 mising that the experiments of Mme. Curie and 

 Debierne will settle this question conclusively. No 

 doubt, an interval must elapse to allow the polonium 

 to decay before the final examination of the residual 

 substance can be made. E. Rutherford. 



I HE DISCOVERY OF A SKELETON OF 

 PALEOLITHIC MAN. 

 T\R- CAPITAN and M. Peyrony are to be con- 

 -L^ gratulated on another important discoverv of the 

 ■remains of Palaeolithic man on September 17, at 

 Ferrassie, in Dordogne, a locality which has been 

 made famous by the investigations of M. Pevrony 

 during the past decade. Here he has discovered and 

 studied five distinct layers, each containing the arti- 

 facts and animal remains of as many well-defined 

 epochs. In ascending order these are : — (i) .^cheu- 

 lian. (2) Mousterian, (3) Lower Aurignacian, (4) Middle 

 .•\urignacian, and "(5) Upper Aurignacian. The 

 skeleton, which is described by Dr. Capitan in La 

 Nature for December 25, 1909, was found between the 

 NO. 2104, VOL. 82] 



layers i and 2, and as these and the three upper 

 layers were absolutely intact, it is certain that the 

 remains belong to the Mousterian epocli. The first bones 

 seen were the ends of a tibia and femur, and before 

 excavating further an invitation was sent to a num- 

 ber of French archaeologists to witness the exhumation. 

 With infinite care and precautions, an entire skeleton 

 was revealed. It lay on its back, with the trunk 

 turned slightly to the left; the legs were strongly 

 flexed, the knees being turned to the right; the left 

 arm was extended along the side, with the hand at the 

 hip; the right arm was flexed, the hand being near 

 tlie shoulder, and the head was turned to the left, the 

 mouth being open. 



The skeleton was photographed in situ. Around, 

 above, and beneath were a large number of bones 

 which had served as food for and had been broken by 

 the Mousterians, as well as teeth of bisons, deer, 

 goats and reindeer; the artifacts included points, 

 knife-scrapers, disks, hammers, and bone-breakers of 

 quartz of the Lower Mousterian-*type (that is, worked 

 on one face only). ^^■■ 



The long and small bones were carefully removed. 

 The pelvis, thorax and skull were severally covered 

 with tinfoil, and plaster was poured around each, so 

 that when the plaster set they could be removed 

 without injury. Thus protected, they were taken to 

 Paris without further damage or loss. The 

 restoration, mounting, and study of the skeleton are 

 being undertaken by Dr. Capitan. As no anatomical 

 details have as yet been given concerning the find, 

 anthropologists will have to wait with what patience 

 Ihey can muster until the investigations arc completed. 



The attention of readers of Nature has been directed 

 at various times to the recent finds of Palaeolithic 

 man, but as this is the first whole skeleton which has 

 been obtained of a Mousterian man, the discovery is 

 one of prime importance. 



There is no reason to doubt that the body was 

 definitely placed where it was found; probably it was 

 placed in a corner of a large rock shelter, and covered 

 with earth, stones, and perhaps branches. The 

 shelter was occupied later by generations of men of 

 the Aurignacian epoch. Finally the overhanging 

 chalk roof fell, and its debris subsequently became 

 covered by a layer of stones and earth five feet in 

 thickness. Thus protected, it has remained for 20,000 

 vears. A. C. H. 



TROPICAL .AGRICULTURE.^ 



n^'HIS work does not claim to be a handbook for 

 •»- the technical man, but to give information of 

 value to students, administrators, and others on 

 tropical crops, and at the same time to present the 

 political and theoretical aspects of the subject. 



Part i. (pp. 1-39) deals with the " Preliminaries to 

 Agriculture." Such topics as soil, climate, labour, 

 transport, capital, supply of water, tools, and plant 

 acclimatisation are briefly discussed, frequently by 

 drawing contrasts between the less known conditions 

 of the tropics and the better known conditions of tem- 

 perate regions. 



Part ii. (pp. 40-141), appro.Kimately half the volume, 

 is devoted to the " Principal Cultivations of the 

 Tropics." This is, in our opinion, the least satisfac- 

 tory portion of the book. The principal industries of 

 Ceylon, with which the author is closely acquainted, 

 are well done. The accounts of rice, coffee, tea, cocoa- 

 nuts, and Para rubber, are admirable, although for a 

 work dealing with the tropics as a whole Ceylon 



> " Agriculturelin the Tropics." An El-mentarj- Treatise. By Dr. T. C 

 Willis. Pp. xv;n 4-222. (Cambridge: University Press, 1909.) Price 



