OoiOBEE 7, 1898.] 



SCIENCE. 



473-. 



expected from its electrolytic dissociating 

 power. 



MEASUREMENT OP THE INTENSITY OF SOUND. 



Instruments for the measurement of 

 sound intensities were described before Sec- 

 tion B at Boston by Professor A. G. 

 Webster and by Dr. J. O. Eeed. In Pro- 

 fessor Webster's instrument the amplitude 

 of vibration of a thin glass diaphragm is 

 measured by the interferometer, the fringes 

 being photographed on a moving plate. In 

 Dr. Reed's instrument the amplitude of 

 vibration of a diaphragm is observed by 

 means of a micrometer microscope focussed 

 upon the tip of a stylus attached to the 

 diaphragm. 



Professor Webster outlined a method for 

 calculating the absolute intensity of the 

 sound (amplitude of the periodic force act- 

 ing upon the diaphragm) from the observed 

 amplitude of vibration. In this outline 

 Professor Webster made use of the equation 

 of motion of a system with one degree of 

 freedom, namely, 



If 



+ 4>«- 



Ae^\ 



'Sow, this equation is, in fact, applicable to 

 any sj'stem vibrating in a given simple 

 mode (i. e., when the period of each particle 

 of the system is the same and its amplitude 

 a one valued function of its position) but it 

 is impossible to determine the coefficient a 

 by static measurements of any kind. The 

 effect of the air which vibrates with the 

 diaphragm can, however, be taken into ac- 

 count so that the coefficient a may be ap- 

 proximately determined, by using as a reso- 

 nator a long air column. However, the 

 results of some determinations by Professor 

 Webster agree quite well with sound inten- 

 sities as measured by Rayleigh. 



W. S. F. 



NOTES ON INORGANIC CHEMISTRY. 



The first number of the Chemical News in 

 September is known as the ' Students' ]S"um- 

 ber,' and is devoted to a description of the 

 chemical departments of the British uni- 

 versities and colleges. It is noticeable at' 

 once that the facilities for chemical study 

 in Great Britain are very far behind those 

 of Germany, and I think we may fairly 

 say below those of America. Probably a 

 dozen or even more institutions could be- 

 found in this country where greater advan- 

 tages are offered than anywhere in Eng- 

 land. Three colleges only have more than 

 one professor in the chemical department,, 

 viz.: Victoria University, Yorkshire Col- 

 lege, Leeds, with a professor in the dyeing 

 department, and a professor in the leather 

 industries department, in addition to the 

 professor of chemistry; Owens College, 

 Victoria University, Manchester, with a 

 professor of chemistry and a professor of 

 organic chemistry ; Glasgow and West 

 of Scotland Technical College, with a pro- 

 fessor of chemistry and a professor of tech- 

 nical chemistry. The Royal College of 

 Science and Royal School of Mines has, in 

 addition to a professor of chemistry, an 

 assistant professor, and King's College has 

 a professor of metallurgy. In the number 

 of teaching force also the British colleges 

 would seem to be deficient. The average 

 number of instructors, including all assist- 

 ants and demonstrators, in the twenty- nine 

 colleges mentioned is less than four, and 

 this average is strongly brought up by 

 Owens College and Yorkshire College, each, 

 of which has a corps of ten instructors, 

 and the University College, Liverpool, with 

 seven. The two former would appear to be 

 the only colleges of Great Britain with ade- 

 quately equipped chemical departments j 

 Oxford and Cambridge hardly seem to be 

 in the race. 



The same number of the Chemical News 

 contains, as its single item of current news^ 



