3*72 TRANSACTIONS OF THE 



ing the degree of heat escaping from the chimney, he found the thermome- 

 ter indicated about 500 degrees of heat. 



Subject for the next meeting : " Warming and ventilating of buildings.'* 

 Adjourned. JOHN W. CHAMBERS, Stc'y pro tern. 



June 9, 1858. 

 A meeting of the Mechanics' Club, was held this, Wednesday, June 9, 

 1858, at 8 o'clock. 



Present — Messrs. Fisher, Stetson, Johnson, Brown, Seeley, Butler, 

 Reynolds, Hedrick, Main, Ingolls — 18 in all, 



Mr. Fisher in the chair. Mr. John W. Chambers was appointed Secre- 

 tary pro tem. 



The following extracts, by Mr. Meigs, from scientific journals were read : 

 [London Athenseum, Feb. 1858. Royal Institution, Jan. 29, 1858.] 



ON MOLECULAR IMPRESSIONS BY LIGHT AND ELECTRI- 

 CITY. 



The remarkable relations existing between the physical structure of mat- 

 ter and its effect upon heat, light, electricity, magnetism, &c., seem, until 

 the present century, to have attracted little attention : thus, to take the 

 two agents, light and electricity, how manifestly their effects depend upon 

 the malecular organization of the bodies subjected to their influence. Car- 

 bon as diamond, transmits light but stops electricity! as coke, or graphite, 

 into which heat transforms diamond, transmits electricity, but stops light ! 

 The celebrated photographer, Mons. Niepce de St. Victor, recently tried 

 the following experiment, viz : An engraving after having been some time 

 in the dark, was then exposed to the light of the sun as to one-half vfhile 

 the other half was covered by an opaqvie screen. It was then taken into a 

 dark room, the screen removed, and the whole engraving placed in close 

 proximity to a sheet of highly sensitive photographic paper, that half of the 

 engraving which had been exposed to the light was reproduced on the pho- 

 tographic paper, while no effect was produced by the other half. 



Mr. Grove had little doubt that if this discourse was in summer instead 

 of mid winter, he could have litei-ally realized in this theatre, the Laputa 

 problem of extracting sunbeams from cucumbers. While fishing last au- 

 tumn, at Fontenay, he observed some white patches on the skin of a trout, 

 which he was satisfied were not there when he was taken out of the water. 

 The trout had been rolling about in some leaves, at the foot of a tree, and 

 this gave him the notion that the effect might be photographic ! He placed 

 a serrated leaf on each side of a fresh fish, laid him down on his side, that one 

 leaf might be exposed to sun light while the other was in dark. After an 

 hour or so, a well defined image of the leaf was apparent on the exposed 

 side, and none on the dark side. Electricity effects molecular changes. 



Of the practical results to science, of the molecular changes, a beautiful 

 illustration was afforded by the photography of the moon, by Mr. De la 

 Rue, which, afforded by the aid of the electric lamp, images of the moon, 

 six feet in diameter, in which the details of the surface were well defined. 

 The cone in Tycho, the double cone in Copernicus, and even the ridge of 



