562 Transa ctions of the American Institute. 



two years, by means of a battery on the system of M. Marie Dary, 

 without being replenished with the sulphate of mercury. It has 

 also been successfully applied to the hospital of Laribosi6re; the 

 allowance of fresh air for each bed being sixty meters per hour, or 

 6,120 meters for one hundred and twenty beds. 



THE SPIROMETER. 



This instrument measures the actual volume of air respired by a 

 pair of human lungs, and as an index of health and vigor. On 

 medical authority it is stated that examinations for life insurance 

 have revealed the fact, that persons who habitually drink ardent 

 spirits between meals, have not the power to blow up the spiro- 

 meter to the point due to their size and weight. By this means 

 individuals, not previously suspected of intemperance, have been 

 detected. 



VESSELS FOR HOLDING HYDROFLUORIC ACED. 



The engraver on glass is often at a loss for utensils to hold his 

 acid, but Stolba mentions that glass and porcelain vessels are pro- 

 tected from the action of hydrofluoric acid {cilaf) by a thin coating 

 of paraffin (a mixture of hydrocai'bons), which is put on by care- 

 full}^ cleaning and heating the vessel, and melting some paraffin in 

 it, and moving it until the whole surface is covered, when the 

 excess of paraffin is poured off. By this plan, both lead and gutta 

 percha vessels may be dispensed Avith. 



EXPANSION OF CRYSTALS. 



A very ingenious plan for determining the coefficient of expan- 

 sion has been devised by Fitzeau. He gives the formula express- 

 ing the expansion in any direction, as well as the cubical expansion; 

 and having determined the expansion in the direction of one of the 

 three axes of a ciystal at twenty degrees, forty degrees and sixty 

 degrees C of heat, he deduces the expansion for each degree. The 

 crystal to be measured is placed with one side on a platinum sup- 

 port, and a polished glass plate is arranged above the surface, leav- 

 ing a small interval. By means of an alcohol flame, with salt, he 

 produces the Newtonian rings; with the aid of a telescope he 

 counts the number of fringes passing beyond certain fixed points 

 of the support, and notes the changes made by the application of 

 heat. 



HYDROCARBONS FROM HERRING. 



The distinguished American chemists, Messre. Warren & Storer, 

 have obtained from menhaden oil, an animal fat contained in the 



