36 



described by Mr. Barnes, as U. alasmodontina, and by Mr. 

 Lea, in ill Trans. Am. Philos, Soc. as symphynota compres- 



Joseph Henry read a communication on the production of 

 cold by the rarefaction of air, accompanied with experiments. 



One of these experiments most strikingly illustrated the 

 great reduction of temperature which takes place on the sud- 

 den rarefaction of condensed air. Half a pint of water was 

 poured into a strong copper vessel, of a globular form, and 

 having a capacity of five gallons — a tube of one-fourth of an 

 inch in caliber, with a number of holes near the lower end, 

 and a stop-cock attached to the other extremity, was firmly 

 screwed into the neck of the vessel : the lower end of the tube 

 dipped into the water, but a number of the holes were above 

 the surface of the liquid, so that a jet of air mingled with wa- 

 ter might be thrown from the fountain. The apparatus was 

 then charged with condensed air, by means of a powerful con- 

 densing pump, until the pressure was estimated at nine atmos- 

 pheres : during the condensation, the vessel became sensibly 

 warm. After suffering the apparatus to cool down to the 

 temperature of the room, the stop-cock was opened ; the air 

 rushed out with great violence, carrying with it a quantity of 

 water, which was instantly converted into snow ; after a few 

 seconds, the tube became filled with ice, w^hich almost entirely 

 stopped the current of air. The neck of the vessel was then 

 partially unscrewed, so as to allow the condensed air to rush 

 out around the sides of the screw ; in this state, the tempera- 

 ture of the whole atmosphere was so much reduced, as to 

 freeze the remaining water in the vessel ; the stop-cock and 

 tube at the same time became so cold, that the ringers adhered 

 to them in the same manner that they are sometimes found to 

 stick to the latch of a door, on an intensely cold morning. 

 This experiment was exhibited to the Institute within six feet 

 of a large stove, and in a room, the temperature of which was 

 n.v I-- <; ... , , ' . _ r , [ -\ fhf nn.-rnHf-i . 



March 16. Frederick Matthews read the first part of an 

 historical account of the Literary Institutions of the United 

 States. 



L. C. Beck concluded the reading of his paper on lead 



In rhis paper the author commenced with a notice of the 

 various ores of lead, among which the sulphuret (galena) was 

 particularly alluded to, as being the richest of all the ores, and 

 in fact the" only one that is extensively worked. The sub- 

 species and varieties of galena were briefly described ; and 

 the peculiarity observed by Williams in his Natural History 



