November 15; 1907] 



SCIENCE 



673 



steam engine judiciously constructed, was 

 practically demonstrated some time ago by S. 

 P. Langley. More would, therefore, be ex- 

 pected from the gas engine, if constructed 

 with equal forethought. I have always had 

 some misgivings, however, as to whether these 

 experiments, into which so much devoted 

 labor was put, actually met the real issue in- 

 volved. It seemed to me that they proved 

 that the power available in case of the ordi- 

 nary engine is just about sufficient to main- 

 tain flight and no more; whereas a really 

 practical machine should be provided with a 

 motor whose output of work per second and 

 per kilogram of weight, could be made 

 enormously to exceed the demands upon it, 

 under conditions of smooth soaring. 



If one is in search of a maximum of power 

 combined with a minimum of weight, one in- 

 voluntarily looks to some form of modem ex- 

 plosive and in particular to those which can be 

 worked up into wicks or ribbons. These could 

 be adapted for use in connection with the 

 rocket principle which has so frequently 

 stimulated the imagination of inventors, in a 

 way to require the least amount of subsidiary 

 mechanism. In fact, such expansion is vir- 

 tually its own propellor. The only question 

 is, how can this quite prohibitively excessive 

 power be controlled. In other words, how 

 may the enormous per second expenditure of 

 energy be reduced in any desirable amount at 

 will, and compatibly with safety and the need 

 of the operator? 



Now it occurred to me that in case of the 

 nitrogen explosives there may be a method of 

 obtaining a continuity of power values within 

 safe limits from insignificant amounts up to 

 the highest admissible, by using some appro- 

 priate method of very cold storage. It is well 

 known that at sufficiently low temperatures 

 phosphorus and oxygen cease to react on each 

 other, that fluorine is indifferent to hydrogen, 

 etc. Is it not, therefore, probable that an 

 explosive tendency will be toned down as 

 temperature decreases ; or that a molecular 

 grouping which is all but unstable at ordinary 

 temperatures will become stable at a tempera- 

 ture sufficiently low, and proportionately stable 

 at intermediate temperatures. This is then 



the experiment which I would like to see tried, 

 the endeavor to get a gradation of power 

 values ending in prohibitively large maximum, 

 by the cold storage of explosives. If it suc- 

 ceeds, it seems to me that a motor yielding per 

 pound weight not only all the power needed 

 in the flying machine under any emergency 

 will be forthcoming, but that large amounts 

 of the inevitably dangerous source of such 

 power may be taken aboard for use en route. 

 The lower temperature of the upper air would 

 here itself be an assistance. 



Carl Barus 

 Beown University, 

 Providence, R. I. 



ABSTRACTS FOB EVOLUTIONISTS 



ANTARCTIC APTERA 



Professor George H. Carpenter has re- 

 cently published' a report on the Collembola 

 of the South Orkney Islands, obtained by th« 

 Scottish national Antarctic expedition. In 

 describing Isotoma hrucei n. sp. he remarks 

 that it is closely related to the Arctic and 

 subarctic I. heselsii Packard : " In the general 

 build of the body and the structure of the 

 spring — particularly the form of the mucro, 

 with its three prominent claw-like teeth — these 

 two species of Isotoma stand apart from all 

 other members of the genus." After discuss- 

 ing the distribution of the Antarctic Collem- 

 bola, Professor Carpenter arrives at the con- 

 clusion that the ancestor of I. hrucei must 

 have reached the Antarctic lands during the 

 secondary period, and that during aU the time 

 that has since elapsed, it has undergone no 

 more modification than is expressed by the 

 difference between I. hrucei of the south and 

 I. heselsii of the extreme north — a difference 

 of much less than generic value. 



UNIONID^ OF THE LARAMIE CLAYS 



It is well known to naturalists that the 

 eastern United States are the home of nu- 

 merous remarkable groups of fresh-water mus- 

 sels, which are absent from the western part 

 of the continent, and to all appearances orig- 



^Proe. Roy. Sac. Edinburgh, XXVI., Part VI. 

 (1906). 



