8 The Period from 185 i to i860 



(Charleston) meeting consist of 215 pages, while there are 414 pages in the 

 Proceedings of the New Haven meeting. The membership of the Associa- 

 tion at the Charleston meeting was 634 ; at the New Haven meeting it had 

 become 684. On August 22 Joseph Henry, president of the Association for 

 the preceding year, delivered an address as retiring president, but it was not 

 written and the title of it is unknown. 



II. THE PERIOD FROM 185 1 TO i860 



In order not to become involved in the endless details of individual meet- 

 ings which have lost much of their importance with the passing of time, the 

 history of the Association and the progress of science will be sketched by 

 decades. The decade 1850- 1860 is the first one after the Association had 

 been organized and the pattern of its meetings established. 



Several great scientific discoveries and generalizations had been made 

 in the decades immediately preceding the one under consideration. One of 

 the most important of these generalizations was Dalton's atomic theory 

 (1808) based on Proust's experimental discovery of the law of multiple 

 proportions in chemical reactions. This basic theory for chemistry was 

 supplemented in 181 1 by Avogadro's inference, or hypothesis, that equal 

 volumes of different gases at the same temperature and under the same pres- 

 sure contain the same number of molecules. The synthesis of urea by 

 Wohler, in 1828, assured chemists that the laws of their science hold also in 

 the organic field. 



In the field of geology a new era was inaugurated by the publication of 

 the three volumes of Lyell's Principles of Geology in 1830, 1832, and 1833. 

 A reasonable basis- for the long periods of time required by Lyell for the 

 geological processes was provided in the Nebular Hypothesis of Laplace, 

 published first in 1796 and in a somewhat expanded form in 1806. The law r 

 of the conservation of energy was formulated almost simultaneously by 

 Robert Mayer and James P. Joule, in 1842. In 1847 Helmholz extended it 

 to the organic world. It was in the middle part of the first half of this 

 century that Faraday and Joseph Henry discovered the relations between 

 electricity and magnetism. It was in this period that the cell theory of the 

 structure- and functioning of living organisms took form, the papers of 

 Schleiden and Schwann appearing in 1838-39. It was in the latter part of 

 this half century that the principles of organic evolution began to take form 

 in the minds of Darwin, Wallace and Spencer. As to inventions, Morse pro- 

 duced the telegraph in 1836; Daguerre first made photographs in 1839; 

 and Long, Wells, Morton, and Simpson introduced the use of ether, nitrous 

 oxide and chloroform, for producing anesthesia, in the years 1842 to 1847. 

 Great scientific discoveries in the half century preceding the organization of 



