34 PROCEEDINGS OF THE AMERICAN ACADESIY 



Mr. Charles Jackson, Jr. said that actual experiments by 

 the thermometer have proved that 360^ of heat are saved by 

 the regenerator, there being only 30^ difference between the 

 temperature of the air going out and that going in. 



Professor Gray alluded to a very interesting botanical dis- 

 covery in this country, namely, the finding of two species of 

 Trichomanes in the northwest corner of Alabama ; species 

 of a group of ferns, of very delicate texture, usually con- 

 fined to very moist parts of the tropics, or to islands having 

 a damp climate and equable temperature, but not before known 

 to occur within the limits of the United States. 



The small species of Trichomanes exhibited by Dr. Gray 

 is doubtless a new species, which he proposes to name T. 

 Petersii, in honor of the discoverer, T. M. Peters, Esq. The 

 other is the Trichomanes radicans, found in the south- 

 western parts of Ireland, and also widely scattered in the 

 tropics. Dr. Gray mentioned that the latter is very frequently 

 cultivated in the glazed cases invented by Mr. Ward ; with- 

 out such treatment it is incapable of cultivation. 



The wide range of the ferns having been alluded to, a dis- 

 cussion arose on the difficult question of specific characters. 

 Many supposed identical species of animals have been found, 

 on close examination and actual comparison, to be different ; 

 and it was questioned whether the same may not be true of 

 the cosmopolite ferns. 



Three hundred and seventy-seventh meeting. 



April 5, 1853. — Monthly Meeting. 



The President in the chair. 



Professor Horsford made some remarks explanatory of a 

 part of the fourteenth chapter of Leviticus, in which are de- 

 scribed the signs and treatment of " leprosy " in a house. 



He alluded to the decomposition of sulphate of iron when 

 subjected to decomposing animal matter, and its change into 

 the sulphuret or iron pyrites. This last oxidates readily, and 



