PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 825 



rated by forcible rupture, however, this interlinking cannot bo 

 restored, owing, probably, to the interposition of gaseous mole- 

 cules, the inequalities of the surface, and, perhaps, to some modi- 

 fications of the forms of external orbits, by which there-adjustment 

 of the corresponding poles, without passing through the prepara- 

 tory liquid state, is rendered impossible. The distances betM'een 

 the orbits of the two bodies are now immensely inci'eased. so as 

 to become apparent even to the senses, and the law of the inverse 

 squares would seem sufiicient to account for the enormous diminu- 

 tion of the attractive force. 



Bridge Building. 



This selected subject for discussion, was taken up by Mr. Alfred 

 Boiler, C. E., who, in a speech of half an hour, rapidly sketched 

 the progress of bridge building in America, confining his remarks 

 principally to the immense structures on our various railways. 

 Some of the advantages and defects of the systems now in use 

 were pointed out. He illustrated, by diagrams on the blackboard 

 the lines of pressure and resistance, and suggested various improve- 

 ments. A high compliment was paid to American o-enius as 

 evinced in the great railroad bridges ot this country. It is to be 

 regretted that no report of Mr. Boiler's remarks Avas made at the 

 time. 



The association decided to take up the subject of bridge build- 

 ing at a future meeting. Adjourned. 



American Institute Polytechnic Association, ) 

 February 2Wi, 1867. ' \ 

 Prof. S. D. Tillman, in the chair ; T. D.- Stetson, Esq., Sec'y. 

 The following notes on science and art vrere presented by the 

 Chairman : 



Thread from the Cotton Stalk. 

 An ingenious person in New Orleans has made from the stalk 

 of the cotton plant a fine strong thread, resembling that made from 

 flax, which he proposes to use in the manufacture of cloth. 



Solar Heat. 

 Prof. Benjamin Pierce, of Harvard College, has shown, without 

 resorting to the meteor theoiy for souices of replenishment, that 



