ISO Miscellanies. 



6. Heat produced by the compression of gas. — In the June No. of 

 the Ann. de Chimie et de Phys. Baron Thenard publishes some ob- 

 servations on the hght which is emitted from air and from oxygen by 

 compression. Common air, oxygen and chlorine, are the only gases 

 which are known to emit light when compressed. Hydrogen, azote 

 and carbonic acid, afford no such phenomena. Thenard, presuming 

 that this difference might arise from the combustion of the oil or 

 grease with which the piston of the compressing machine is impreg- 

 nated, performed the experiment so as to avoid this source of error, 

 by using a piston of potter's felt, well moistened with water, after 

 having washed the tube well with potash to remove the grease. 

 There was then no light, how forcible soever the compression of oxy- 

 gen gas ; but at the same time, if a piece of paper or dry wood, were 

 attached to the end of the piston, there was a vivid inflammation in 

 the same gas. Chlorine presented the same results. Thus no gas 

 becomes luminous by simple compression in the pneumatic fire 

 pumps. It was ascertained that a fragment of pine wood would not 

 inflame in oxygen gas at the temperature of 350° cent, under atmos- 

 pheric pressure. It only became of a deep brov/n color, but it inflam- 

 ed at 252° under a pressure of 260 centimetres. 



To determine the temperature to which compression would elevate 

 other gases, M. Thenard used fulminating powders which exploded 

 at different temperatures. He thus ascertained that a gas compressed 

 as strongly as possible by hand in a glass tube, rises much beyond 

 205° centigrade (or 401° F.) Powders which decompose at 205° 

 cent, explode in azote, hydrogen and carbonic acid by sudden and 

 strong compression. — Ibid.. 



7. The seat of taste. — By covering the tongue with parchment, 

 sometimes in whole, and sometimes in different parts, it has been de- 

 termined by two experimenters in Paris, M. M. Guyot and Admy- 

 raula, that the end and sides of the tongue, and a small space at the 

 root of it, together with a small surface at the anterior and superior 

 part of the roof of the palate, are the only portions of surface in the 

 cavity of the mouth and throat, that can distinguish taste or sapidity 

 from mere touch. A portion of extract of aloes, placed on any other 

 part, gives no sensation but that of touch, until the saliva carries a 

 solution of the sapid matters to those parts of the cavity. — Ibid. 



8. Currents in the ocean, by Charles Riiviker, Esq. — " The wa- 

 ters of the Pacific being supposed higher than those of the Atlantic, I 

 expected an easterly current on approaching Cape Horn, but I could 

 discover none. Near the northern coasts of the Brazils and Guiana,^ 



