Contents. xi 



BY IIOBERT E. C. STEAliNs^. 



On IMix aspersa in Culifornia, aud the Geographical Distiibution of 

 certain West Americau Laud-Snails, and previous errors re- 

 lating thereto T 129 



BV liOBEKT JI. TIIUl:^^TON. 



The place of Sadi Carnot in the History of Thermotics 19 



Note relating to a newlj- discovered Absolute Limit to Economical Ex- 

 pansion in Steam Engines , 353 



HY EDAVAlil) V(.»N MAiiTEN^. 

 Descriptiou of two Species of Land-Shells from Porto Rico 370 



BY W. WALTER WEBB. 

 Index to the Literature of Electrolysis (1784 to 1880) 313 



BY It. P. WHITFIELD. 



Descriptions of New Species of Fossils from Ohio, with Remarks on 



some of the Geological Formations in which they occur 193 



BY F. <K AVIECTLMANN. 

 Fusion-Structiu-es in Meteorites (with Plates XIX, XX, and XXI) 289 



BY HENRY S. WILLIAMS. 



The Life-History of Spirifer Iceuis, Hall ; a Palseoutological Study (with 



Plate XIV) 140 



