IXDUSTKIAL PROGRESS DURING THE YEAR 1873. xxxvil 



has made known a method of analysis of sounds, and has ap- 

 plied it to the investigation of the complicated sounds that 

 occur in nature. Especial interest attaches to his investiga- 

 tions on the antennae of insects, considered as the organ of 

 hearino\ 



The interesting phenomena of the vibration of cords at- 

 tached to and vibrating with a diapason have been investi- 

 gated with much success by Mercadier and Gripon. 



Professor Henry has continued his observations on abnor- 

 mal phenomena of sound in connection with fog signals. 



Barrett has investigated certain remarkable molecular 

 changes occurring in iron Avire at a low red heat, by wdiich it 

 appears that instead of expanding continuously for every ad- 

 ditional degree of heat imparted to it, there is a certain tem- 

 perature corresponding to the red-hot state at which a sud- 

 den contraction takes place when the wire is being heated ; 

 but a sudden elonoation is observed when the wire is being: 

 cooled. Barrett associates these phenomena with others ob- 

 served by Tait in thermo-electric experiments, and concludes 

 that both lines of inquiry show that a profound molecular 

 disturbance takes place in iron at a low red heat. 



CHEMISTRY AND METALLURGY. 



During the j^ast year much has been done in all depart- 

 ments of Chemistry. In chemical physics, especially, good 

 work has been accomplished. The field of thermo-chemistry 

 has been considerably enlarged, the chief workers in it being 

 Thomson and Berthelot. Thomson has investis^ated the af- 

 linity of hydrogen for the non-metallic elements, the formation 

 and decomposition of formic acid, and the formation of tlie 

 sulphur acids. The first and last named investigations have 

 led to the most interesting results, perhaps, it being shown on 

 the one hand that the affinity of hydrogen for the first mem- 

 ber of each of the four natural groups of non-metallic ele- 

 ments is positive, but diminishes with the higher members as 

 their atomic weights increase; and, on the other hand, that 

 the total heat of formation of the sulphur acids decreases 

 Avith every additional atom of sulphur. Berthelot's Avork 

 lias been mainly on the state of various salts and of the hy- 

 dracids in solution in Avater. As regards salts, confirmation 

 is given of the vicAv that Avhen two salts react upon each oth- 



