March. 1911. 



KNOWLEDGE. 



115 



whether it be the eye or a quartz photographic leus, that a 

 violet glow is visible in the air in the neighbourhood. It 

 appears that this glow cannot be accounted for by either 

 fluorescence of the gas in which the spark occurs, or by the 

 scattering of the light by dust or moisture particles. The 

 phenomenon is very curious. 



The ultra-violet rays are obtained in profusion from the 

 mercury arc, pro\ided the walls of the tube are of Jena 

 ■' Uviol " glass or quartz : in fact, the rays from these lamps, 

 unless cut off by glass, by which they are absorbed, are most 

 injurious to the eyes. It appears that one single wave-length 

 of the light is capable of penetrating the cornea of the eye and 

 of doing the mischief. 



MM. Urbain, Seal and Feige have devised a mercury lamp 

 which gives a pure white light. Taking advantage of the high 

 melting-point of tungsten they have employed an arc between 

 mercury as kathode and tungsten as the positive pole of the 

 arc. The arc is maintained in a vacuum, and the tungsten 

 is only slightly separated from the surface of the mercury. 

 The tungsten gets white hot. while the usual good efficiency 

 of the mercurj- vapour lamp is attained. 



AFTERGLOW IX \ACLLM TUBES.— The Hon. R.J. 

 Strutt has been investigating with great skill the glow obtained 

 in "vacuum" tubes containing air, which sometimes occurs 

 after the electric discharge is turned off. He removed the 

 air from the neighbourhood of the discharge, and passed it 

 into a tube, where he could observe the glow and examine the 

 conditions which prevented or improved it. He found that 

 those substances which destroy ozone prevented the production 

 of the glow, and. further, that it was necessary to send a 

 discharge through the air before the glow would appear, even 

 if ozone had been added. In this way he has shown that the 

 effect is due to both ozone and nitric o.xide. and is merely a 

 luminescence due to chemical combination, presumably of the 

 nature of the glow obtained on the oxidation of phosphorus. 



Mr. Strutt has found more recently that similar most striking 

 glow phenomena are obtained with nitrogen, a blue glow- 

 being obtained in the presence of iodine, while metals exposed 

 to this nitrogen give out their line spectra. 



THE ANNUAL GENERAL MEETING OF THE 



PHYSICAL see I ET v.— Professor Callendar, F.R.S., at the 

 .Annual General Meeting of the Physical Society, on Friday, 

 February 10th, read a most interesting address on the 

 " Caloric Theory of Heat." He dealt with the much-over- 

 looked and misrepresented work of Sadi Carnot. Carnot 

 began his investigations with the purpose of finding what 

 advantage would be gained by using working fluids other than 

 steam in engines. He was led to the consideration of an 

 ideal heat engine, and showed that if no direct transference of 

 heat occurred between bodies at different temperatures, the 

 transformations of heat and motive power were reversible in 

 such a " cycle." He found that the efficiency of such an 

 engine (or the ratio of the moti\e power to the quantify of 

 heat which produced it) was the maximum possible, and was 

 independent of the working fluids used. By applying the 

 Caloric Theory of heat, Carnot was able to deduce all the 

 relations between heat and work in reversible processes, and 

 to forestall the subsequent determinations of the mechanical 

 equivalent of heat, by utilising the somewhat rough experi- 

 mental data which were at his disposal. 



The idea of Caloric is similar to the idea of quantity of 

 electricity ; if all electrical calculations had to be made from 

 considerations of electrical energy, instead of picturing a 

 quantity of electricity passing from one potential to another, 

 there would be much complication. In the same way, a 

 conception of (juantity of caloric passing from one tempera- 

 ture to another, besides that of the energy equivalent to such 

 an operation, would be valuable in simplifying the underlying 

 notions of that somewhat abstruse subject, thermodynamics. 

 Caloric is only another name for Rankine's " Thermodynamic 

 Function," or Clausius' "Entropy." It would be well to 

 point out that the " Calorie " is a measure of thermal energy, 

 which must not be confused with the '" Carnot." or unit of 

 quantity of caloric. 



Professor Callendar's study of Carnot's work will make it 

 possible to give the student a less abstract conception of heat. 



The addresses of the officers of the Society, previous to the 

 reading of the President's address, testified to the flourishing 

 condition of the Society and to its great activity, while it was 

 hoped that many would be led to share its Tiiary advantages 

 and become members. 



ZOOLOGY. 



By Professor J. Arthur Thomson'. 



RIGHT AND LEFT-HANDEDNESS.— After all the 



discussion on this subject it is rather surprising to hear an 

 anatomist of the rank of Karl von Bardeleben saying that 

 our ignorance on the matter is shameful. We cannot state 

 percentages for different races : we have done little in ' the 

 wav of distinguishing different degrees of left-handedness ; 

 and we do not know how it is that right-handedness has 

 become so predominant in mankind. Perhaps, one sometimes 

 thinks, each species has its particular asymmetry, just as many 

 great types have. The gibbon and orang are right-handed ; 

 the gorilla and chimpanzee are left-handed. To point to 

 asymmetry in the brain, e.g., the stronger backward protrusion 

 of the left cerebral hemisphere, except in typical left-handed 

 people, shifts the problem without solving it. Professor von 

 Bardeleben gives the interesting piece of information that 

 there were last year 119101 in the German army ten thousand 

 three hundred and twenty-two left-handed men. Only 3'88 per 

 cent., however '. 



FERTILE HYBRIDS BETWEEN BISON AND 

 DOMESTICATED CATTLE.— E. Iwanoff refers to the 

 estate of F. E. Falz-Fein, " Askania Nova," where a 

 number of half-breeds ha\-e been produced by crossing 

 Bison ainericanus with domestic cows and with the 

 European Bison {Bison bonasits or eiiropaeiis). Others 

 have been produced — " Three-quarters American Bison and 

 one-quarter domestic Bos taurus, and one-quarter American 

 Bison and three-quarters Bos taurus." The fertility of the 

 half-breed bison females has been proved. They produce 

 offspring to both .\merican bison and European bison. The 

 male half-breds have sexual instincts, but there is no proof of 

 fertility. But the male of three-quarters bison blood seems to 

 be fertile with the domestic cow\ 



OVIPAROUS AND VIVIPAROUS.— It is said that some 

 snakes, such as the grass snake, normally oviparous, may 

 become viviparous in the comfortable conditions of captivity. 

 That is to say tfor the old terms are as bad as they are 

 difficult to dislodge), the eggs may hatch inside the body 

 instead of outside. E. Roubaud has recently reported an 

 interesting parallel case in insects, namely one of the flies, 

 Musca corvina Fabr. In tropical .\frica this fly is constantly 

 viviparous all the year round, and at inter\als of four days or 

 so. It can continue this reproductive regime as long as the 

 average temperature is not less than 30 C. Now the interest- 

 ing point is. that according to Portchinsky. the fly is always 

 oviparous in the north of Russia, laying twenty-four eggs, 

 while in the Crimea it produces a large larva viviparously at 

 the end of spring and in summer. The author calls this 

 " seasonal and climatic poecilogony." 



BRAIN OF A SILVER-FISH.— Comparatively little has 

 been done in the way of comparing the brains of different 

 kinds of insects. One, therefore, welcomes the study which 

 Otto Bottger has made of the brain of the little wingless 

 insect, Lepisiua saccharoides, not uncommon in houses, 

 and popularly known as the " silver-fish." It is something of 

 an achievement to be able to present a picture of the minute 

 structure of the brain of such a tiny creature, and it is 

 interesting to notice the investigator's general result — that the 

 brain of this type is in many ways quite peculiar. Indeed it 

 shows parts which have not been seen as yet in any other 

 insect. 



LARVAL MANTIDS MIMICKING ANTS. — From a 

 pale emerald-green, walnut-sized nest, sent to the Zoological 



