FRAGMENTS OF SCIENCE. 



719 



sympathy, How many young men of your 

 own brotherhood are you willing to sacrifice 

 for each convert ? How many of your own 

 sons will you expose to sure infection 

 and degeneration in the conduct of your 

 philanthropic purpose? Or will you satisfy 

 your own conscience by consenting to the 

 necessary conscription of other people's sons 

 when it presently becomes impossible to 

 maintain our armed forces in those islands 



without a draft ? " Mr. Atkinson says that 

 his attention has been called to this phase 

 of the evil attendant upon military occupa- 

 tion in the course of his social studies. 

 " The greatest and most unavoidable dan- 

 ger," he writes to the commander in chief of 

 our armies, " to which these forces will be 

 exposed will be neither fevers nor malaria ; 

 it will be venereal diseases in their worst 

 i and most malignant form." 



MINOR PARAGRAPHS. 



A new and very ingenious method of 

 space telegraphy is discussed at length in an 

 article by Karl Zickler in the Elektrotech- 

 nische Zeilschrift It depends on a phenom- 

 enon discovered by Hertz in 1 887, viz., the in- 

 fluence of certain short wave-length light rays 

 upon electrical discharges. The ultra-violet 

 waves, which are obstructed by glass but 

 transmitted by quartz, are the most effective. 

 The source of light is an arc lamp. The 

 light is passed through a lens of rock crystal 

 to the receiver. The receiver is a gla^s ves- 

 sel partially exhausted of air, one end of 

 which consists of a truly parallel plate of 

 rock crystal. In front of the receiver there 

 is a condensing lens of rock crystal, and 

 within the exhausted chamber are the two 

 electrodes, one of which is an inclined disk 

 and the other a small ball. The electrodes 

 are connected with the secondary portion of 

 an induction coil, and when the ultra-violet 

 rays fall upon the inclined disk and are re- 

 flected to the ball, a discharge will be pro- 

 duced which may be read either with a tele- 

 phone or a coherer. The signals are sent by 

 alternately interposing a plate of glass in 

 front of the rays issuing from the transmitter 

 and removing it therefrom. Herr Zickler 

 has made many experiments to verify his 

 conclusions and appears to have demon- 

 strated the feasibility of his idea in practice. 



Mr. Dawson Williams has announced in 

 Nature the discovery in many susceptible 

 persons of a periodicity in the effects that 

 follow a sting. The immediate result, he 

 says, is a small flattened wheal, pale and 

 surrounded by a zone of pink injection. 

 This is attended by itching, but both wheal 

 and itching are gone in less than an hour. 

 About twenty- four hours later the part be- 

 gins to itch again, and in a few minutes a 



hard, rounded, deep-red papule appears, and 

 is quickly surrounded by an area of cedema- 

 tous skin. The formication is intense, and 

 in the affected area, while the ordinary sen- 

 sations of touch are dulled, those of temper- 

 ature and painful feelings are exaggerated. 

 In two or three hours the itching diminishes 

 and the oedema disappears, leaving a small, 

 red papule, which itches but little. The 

 phenomena recur, with diminished intensity, 

 in the course of another twenty-four hoars, 

 and may return in this way, growing fainter 

 all the time, in four or five daily repetitions. 

 After these returns have ceased, a small, 

 indolent papule may persist for weeks or 

 months. This periodicity is not observed in 

 all subjects, but most generally in those who 

 suffer most. 



Among the advantages of Linde's liquid- 

 air process, Prof. J. A. Eving, speaking at 

 the English Society of Arts, claimed its giv- 

 ing a means of separating more or less com- 

 pletely the oxygen of the atmosphere from 

 its associated nitrogen. After describing a 

 process by which a liquid consisting largely 

 of oxygen may be produced, the author said 

 that the most interesting application of the 

 liquid which had hitherto been tried on a 

 commercial scale was to make an explosive 

 by mixing it with carbon. When liquid air, 

 enriched by the evaporation of a large part 

 of the nitrogen, was mixed with powdered 

 charcoal, it formed an explosive comparable 

 in power to dynamite, and which, like dyna- 

 mic , could be made to go off violently by 

 using a detonator. The chief advantage of 

 the explosive was its cheapness, the cost be- 

 ing only that of liquefying the air. Even 

 the fact that after a short time the mixture 

 ceased to be capable of exploding might be 

 urged as a recommendation, for if a detona- 



