400 Proceedings of the British Association. 



fixed by gold, by the electrotype process, on the plate, which gives a 

 very perfect copy. "It would be difficult," he says, "to describe in 

 words the beauty and perfection of these ' copper-titlionotypes." 1 The 

 problem of multiplying the Daguerreotype may be now regarded as 

 completely solved." — Prof. Apjohn made a few remarks on this commu- 

 nication, which announced results so different from our received ideas 

 on this subject, it being generally agreed that the chemical rays were 

 the most active in producing the decomposition of the carbonic acid ab- 

 sorbed by the plant. — Mr. Hunt said, that he had listened with great sur- 

 prise to Dr. Draper's paper, as, from his own experiments with colored 

 glasses and transparent media, carefully analyzed so as to determine 

 what rays were absorbed, and what rays passed through them, he had 

 arrived at conclusions diametrically opposed to those now put forth. 

 He acknowledged that he had never tried the experiment with the pure 

 rays of the prismatic spectrum, but he should certainly lose no time in 

 doing so, on his return to England. 



Dr. Tamnau, of Berlin, exhibited some rare miner dlogical specimens : 

 1. A group of Datholite from the neighborhood of Andreasberg, in the 

 Hartz. 2. Two specimens of rose-colored Harmotome from Andreas- 

 berg. The color in these specimens was attributed to the presence of 

 a small quantity of cobalt. They were remarkable for the great size of 

 their crystals, which exhibited not only the usual twins, but also curious 

 and complicated arrangements of three and four, combined according 

 to laws not yet sufficiently understood to allow of their being clearly 

 described. 3. Two very large isolated crystals of Beryl, from Royals- 

 ton, Mass. These were of a beautiful sea-green color, one of them of 

 the usual form, a regular six-sided prism, with the direct terminal face. 

 The other exhibited the faces of the second six-sided prism, of a twelve- 

 sided prism, and of a twelve-sided irregular pyramid. 



" On the Production and Prevention of Smoke,'''' by Mr. Henry 

 Dircks. Mr. D. thought it important to distinguish between open fires 

 and close fires and furnaces. Open fires would always allow an escape 

 of absolute coal gas, and admit atmospheric air to the chimney ; where- 

 as the contrary would be the result with the close fires of the engine- 

 boiler furnaces. He said that the leading fact of consequence, in refer- 

 ence to the smoke, was, that it differed materially from the impure gas 

 evolved from the coal in the furnace. The plans hitherto adopted by 

 manufacturers were chiefly intended to burn smoke, and the great prin- 

 ciple of all such plans was to burn the largest quantity of fuel with the 

 least quantity of air. The error of this method must appear to every 

 one conversant with chemistry. Smoke may be considered as mere 

 carbonaceous matter floating in an atmosphere of the ordinary incombus- 

 tible products of combustion ; the admission of air to this smoke is of no 



