SCIENCE- GOSSIP. 



315 



CONTRIBUTED BY W. H. CADMAN. 



Internal Eesistance op Cells. — It is often 

 qiiestioned whether a galvanic cell has a fixed 

 resistance, even at constant temperature ; and 

 many measui'ements have been made which have 

 been interpreted to show that the internal re- 

 sistance decreases as the current passing through 

 the cell increases. This problem has recently- 

 been attacked by Mr. C. H. Ayres. The bridge 

 method he employed was a modification of Kohl- 

 rausch's well-known method, a telephone being 

 employed to obtain a balance. His results show 

 that in the case of certain galvanic cells the true 

 internal resistance is not a function of the current 

 passing through the cell. 



EUDOLPH KOENIG. — This well-known authority 

 in the science of acoustics died in Paris in October 

 1901. At the age of twenty he learned the trade 

 of musical instrument maker lender the celebrated 

 maker of violins, Vuillaume. He then set up for 

 himself as a manufacturer of acoustical instru- 

 ments. At the London Exhibition of 1862 Koenig 

 first made public his beautiful apparatus for the 

 study of sound waves by means of the manometric 

 flame. He made many important contributions to 

 the science of experimental acoustics, among the 

 best known being his researches on musical tones 

 and on the movement of air in' organ pipes. Even 

 during the latter part of the nineteenth century, 

 when the science of sound was somewhat in the 

 background in consequence of the general interest 

 in electricity, Koenig remained devoted to 'his 

 chosen field. His last investigation was on the 

 '■ Highest Audible Tones and upon the Inaudible 

 Tones up to 180,000 Vibrations per Second." His 

 skill as a mechanician enabled him to turn his 

 extensive theoretical knowledge to practical 

 account. 



Magnetism as a Propulsive Agent for 

 Guns. — Experiments made at Christiania with 

 the electro-magnetic gun invented by Professor 

 Birkeland appear to have given very satisfactory 

 results. The shell is drawn out of the bore and 

 given its initial velocity by means of an electro- 

 magnet, instead of being driven out by the ex- 

 plosion of gunpowder or other explosive agents. 

 The Professor claims that the use of magnetism 

 will enable heavy projectiles to be hurled much 

 farther than by present methods. . The great 

 advantages of this new propulsive agent would be 

 the absolute absence of smoke and noise, in addi- 

 tion to there being no recoil and erosive effects 

 upon the guns, such as those caused by the gaseous 

 products from high explosives. The electro- 

 magnetic apparatus would require to be compact 

 for practical purposes, while powerful enough to 

 give the high velocity of projection needed. 

 Should this difliculty be overcome, a strange com- 

 parison might be drawn between the battles of the 

 past and the battles of the future. The absence 



of noise aiid smoke in battle would enhance the 

 demands for skill and courage, and surround a 

 fight with myster3\ Those interested in military 

 operations will closely follow any developments in 

 this new research. 



Electric Kesistance Furnace. — Professor 

 Holborn, of Berlin, has constructed an electric 

 resistance furnace which enables temperatures up 

 to 1,500° C. to be attained by using an ordinary 

 110-volt electric supply. The curi^ent passes 

 through a resistance coil of platinum or nickel 

 wire wound round a thin porcelain cylinder in 

 which the substance to be heated is placed. The 

 temperature can be easily regulated, so that the 

 furnace should prove especially useful for organic 

 combustion work. 



Wireless Telegraphy. — Writing in " Physik- 

 alische Zeitschrift," III., No. 7, Professor F. 

 Braun, of Strasburg, gives a paper on wireless 

 telegraphy founded upon expei'iments of his own 

 at that city in 1898. These were continued the 

 following year at the mouth of the river Elbe, 

 communication being between Cuxhaven and a 

 lightship at sea about twenty-eight miles away. 

 Other messages were conveyed to. Heligoland, 

 about double that distance. Kesonance of the 

 receiver was one of the chief objects of study. 



Fahrenheit's Thermometer. — The current 

 number of '■ Knowledge " contains an interesting- 

 note by Sir Samuel Wilks, F.K.S., on the history 

 of Fahrenheit's thermometer. He states that it 

 owes its origin to the invention of a thermometer 

 by Newton. This was a tube filled with linseed 

 oil, the starting-point being the temperature of the 

 human body, which was called 12. Newton divided 

 the space between the freezing-point and this 

 into twelve parts. Fahrenheit, in order to read 

 Newton's instrument more accurately, first divided 

 each degree into two parts. Then, finding he 

 obtained a lower temperature than hitherto by a 

 freezing mixture of ice and salt, he took this for 

 his starting-point and counted 24° up to body 

 heat, making 8 his freezing-point, and calling 

 boiling water .53. He afterwards divided each 

 degree into four parts, and thus arrived at the 

 thermometer now in use. 



Kelation between Density and Refractive 

 Index. — The " Physical Review " for January 1902 

 contains an article on the relation between density 

 (fZ) and index of refraction (w) of air by Henry G. 

 Gale. Although the density of a gas can be given 

 a wide range, the index of refraction differs but 

 little from unity, and its variation with changes 

 of density is small. The author employed a modi- 

 fied interference method for his experiments. The 

 pressure of the air was determined by applying 

 the inverse principle of the McLeod gauge. Stout 

 tubes, closed at each end with plate-glass, were 

 employed for confining the air whose index of 

 refraction was to be found, one of the tubes being- 

 connected to the tank which contained the air 

 under investigation and to the pressure gauge. 

 The conclusion arrived at is that, if there is any 

 departure from the law of Gladstone and Dale, up 

 to twenty atmospheres in the case of air, this 

 departure does not amount to more than about 

 •1 per cent. Gladstone and Dale proposed the 



very simple relation — ~ = const, which would 



be expected if transparent substances owe their 

 refractive power to their molecules alone. 



