434 



KNOWLEDGE & SCIENTIFIC NEWS. 



[May, 1906. 



brium, the subsequent decay would follow the exponential 

 law, falling to half value in about 3-7 days. If at intervals the 

 tube is heated to a high temperature and retested when cool, 

 it is found that there is a temporary fall in the activity followed 

 by a gradual recovery. The curve of decay is now not an 

 exponential curve, but consists of such a curve in which 

 a series of notches or depressions are produced ; in other 

 words the recovery is such that the same point of the diagram 

 is ultimately returned to as would have been reached if no in- 

 termediate heating had taken place. The inference that can 

 logically be made is that some part of the contents of the tube 

 ismodified by the high temperature; the results are consistent 

 with the explanation offered by Curie and Dannethat the rate 

 of decay of radium C is increased by high temperature. In 

 examining this conclusion it is important to recollect that in 

 the disintegration of the emanation and of radium A and B, 

 no Beta particle is emitted ; at least none is emitted with suffi- 

 cient velocity to produce any ionisation ; so that the activity 

 measured is chiefly due to radium C. The interpretation 

 then is that the amount of radium C falls olf more quickly at 

 the high temperature, so that when the tube is cooled the 

 contents are nu longer in radioactive equilibrium ; that is to 

 say, radium C is then produced (from Bl faster than it 

 decays : hence it increases in amount, and, if time enough be 

 given, the same equilibrium proportion will be reached as if 

 no heating had taken place. This is a possible explanation 

 (and Mr. Makower only claims it as a possible one); it would 

 be well to test it under conditions in which all ambiguity 

 would be removed. .Vnother explanation would be that 

 radium B broke up less ([uickly at the high temperature, for 

 this would diminish the rate of formation of radium C, and 

 cause therefore a temporary diminution of Beta-activity, 

 the old state of things being gradually returned to on re- 

 cooling. In any case there now can be no doubt that radio- 

 active equilibrium, as well as chemical equilibrium, is effected 

 by temperature ; but the amount of dependence upon tempera- 

 ture is of very different degree in the two cases. 



Refractivities of Vapours. 



Mr. E. B. R. Prideaux recently succeeded in producing 

 hexafluorides of sulphur, selenium, and tellurium, and has 

 investigated their properties. Their refractivities were deter- 

 mined for him by Messrs. Cuthbertson and Metcalfe by 

 means of an interference method. The interest of the results 

 arises in connection with the possibility of calculating the 

 refractivity of a compound from the values for its constituents 

 by simple addition. It is found that for this series of similar 

 compounds there is no approach to an addition law. The 

 values of the refractivities determined are in the proportion 

 of 783. 895, and gyi on the same scale as that for which the 

 value for an atom of fluorine is c)6, of sulphur 540, of selenium 

 810, of tellurium 1350. The values calculated from the addi- 

 tion law for the three compounds are 11 16, 13S6, and 1926 

 respectively; comparison of these with the experimental 

 values shows very marked divergence. The experimental 

 values, on the other hand, are connected with one another by 

 a linear law ; that is to say, if these values are plotted against 

 the densities of the vapours to which they relate, the points 

 obtained lie in a straight line. This is the first series that has 

 been examined in this way. 



National Physical Laboratory Researches. 



.\mongst the numerous researches which have been carried 

 out during the past year, we notice a redetermination of the 

 melting point of platinum by Dr. Harker, which is now found 

 to be 1710° C. within five degrees. Some experiments by 

 Holborn and Henning at the Keichanstalt, published in 1905, 

 give the figure 1710' C. also. Thus it seems clear that the 

 value 17S0 usually accepted is 70 degrees too high. 



.'\n important series of determinations of the calorimetric 

 properties of steam is being made by Mr. Jakeman. After 

 overcoming difficulties mainly concerned with the efficient 

 control of the radiation, he has succeeded in obtaining the 

 specific heat of steam at 4^3 atmospheres pressure, and tem- 

 peratures ranging from 30 degrees C. to 130 degrees C. above 

 saturation. He hopes now to go on to other pressures and 

 temperatures. The Committee are indebted to the Man- 

 chester Steam Users' Association for funds to help with this 

 work. 



ZOOLOGICAL. 



By K. Lydekker. 



Hairs in Amber. 



The insects preserved in amber have loni; since been care- 

 fully studied and described, willi the result that in most 

 cases they have been found to approximate very closely 

 to living types. A new feature is, however, the di.scovery of 

 hairs of mammals in this fossil resin which have recently 

 engaged the attention of a Cierman naturalist. So far as 

 can be determined, such hairs as have at present been 

 examined appear to belong to dormouse-like rodents, 

 although, as it has not yet been found possible to identify them 

 with those of any known genus, it has been suggested 

 that they indicate an extinct ancestral type. .'\ssuming 

 their describer to be right in this view, it is satisfactory to 

 find that he has not considered it necessary to give to the 

 hypothetical rodent thus indicated a distinct name : and it 

 is much to be hoped that the same course will be followed 

 by liis successor in this line of research. For if dormice 

 or other mammals were named on the evidence of their 

 fossilised hairs, there would be no possibility of correlating 

 species thus named with those founded upon the evidence 

 of bones or teeth, with the result that zoological nomencla- 

 ture would become still further involved without any com 

 pensating advantage. 



Flying Snakes. 



Although the alleged flying powers of certain Malay 

 frogs is now generally considered to be a myth, according 

 to Mr. R. Shelford, who recently read a note on the sub- 

 ject before the London Zoological Society, three tree-snakes 

 from Borneo are stated by the natives (and native testimony 

 has, very generally at least, a foundation of truth) to be 

 possessed of the power of taking flying leaps from the 

 boughs of trees to the ground. The snakes in question, 

 which belong to two distinct groups, are respectively 

 named Chrysopelca ornata, C. chrysochlora, and Dcndro- 

 pliis pictus. In ali three of these, the scales on the lower 

 surface of the body are provided with a suture or hinge- 

 line on each side; and by means of a muscular contraction 

 tliese scales can be drawn inwards, so that the whole lower 

 surface becomes quite concave and the snake itself may be 

 compared to a rod of bamboo bisected longitudinally. By 

 experiments on C. ornaia it was seen that the snake when 

 falling from a height descended not in writhing coils, but 

 with the body held stiff and rigid, and that the line of the 

 f.dl was at an angle to a straight line from the point of 

 departure to the ground. In the author's opinion it is 

 liighly probable that the concave ventral surface of the 

 snake helps to buoy it up in its fall ; as it can be sh^wn 

 that a longitudinally bisected rod of bamboo falls more 

 slowly than an undivided rod of equal weight. 



The Largest Frog. 



Hitherto the " record " in the matter of size, so far as 

 frogs are concerned, has been held by Sana guppyi, a 

 species discovered by Dr. Guppy in the Solomon Islands. 

 The record is, however, now claimed for a species from 

 the Cameroons which has been named Sana qoliath, w'hose 

 head and body measure no less than ten inches. 



R-evival of an Obsolete Name. 



.Another instance of a perfectly unnecessary attempt to 

 disturb a generally accepted and well-known name is 

 afforded by the proposal that the Japanese deer should be 

 known as Cervus nipon in place of Ccn-iis sica. It appears 

 that the naturalist, Temminck, gave both names, replacing 

 the first by the second, as being more appropriate. ."M- 

 though such changes would not now be tolerated, it was a 

 common practice among the earlier naturalists, who thought 

 themselves fully justified in so doing. .'\nd if this was the 

 opinion and practice at the time, what is our justification 

 for saying that it is illegitimate? 



