C. GENERAL PHYSICS. 161 



vertinoj a certain known fraction of a sonorous vibration into 

 heat. 



Professor Mayer now exhibited to the Academy the re- 

 sultant curve produced by combining the first six harmonics 

 of a musical note. This curve was then drawn on a circular 

 disk of glass by removing from its blackened surface the 

 continuous line of the curve, which returned on itself. This 

 curve was now placed in front of a lantern, and the image of 

 the line w^as projected on a screen. A slit in a piece of card- 

 board having been placed in front of the curve, and in the 

 direction of a radius of the disk, and the disk being revolved, 

 caused the spot of light on the screen to vibrate like the 

 drum of the ear w^hen it listens to a musical note. This ex- 

 periment, from its novelty and interest, elicited great ap- 

 plause. 



Professor Mayer then proceeded to give an account, illus- 

 trated by experiment, of Avhat he supposes to be the organ 

 of hearing in insects. Placing a male mosquito under the 

 microscope, and sounding various notes of tuning-forks in 

 the range of the sounds given by the female mosquito, the 

 various fibres of the ^tenn^ of the male mosquito vibrated 

 symjDathetically to these various sounds. The longest fibres 

 vibrated sympathetically to the grave notes, and the short 

 fibres vibrated sympathetically to the higher notes. The 

 fact that the nocturnal insects have highly organized anten- 

 na?, while the diurnal ones have not, and also the fact that 

 the anatomy of these parts of insects shows a highly devel- 

 oped nervous organization, leads to the highly probable in- 

 ference that Professor Mayer has here given facts which form 

 the first sure basis of reasoning in reference to the nature of 

 the auditory apparatus of insects. N.Y. Tribune Extra, 

 JSFoAO. 



A SYSTEM OF OPTICAL TELEGEAPIIY. 



During the siege of Paris by the German armies, a Com- 

 mission was nominated by the Governor to decide upon the 

 problem of optical telegraphy. Tlie proceedings of this Com- 

 mission w^ere, of course, not jDublished so long as the public 

 safety demanded secrecy ; but there was deposited with the 

 Secretary of the Academy of Sciences a sealed package, con- 

 taining a short exposition of the experiments and results ob- 



