PrOCEEDIXGS of hie PlIOTOGRAPniCAL SeCTIOiX. 1071 



filter, and wlien ^ranted for use, dissolve in seven ounces of aleoliol, 

 one liuudred and ninetv-two g-raifis of silver. If tlic nlcohol is fully 

 ninetv-fivG per cent, it may require to 1)e wanned a little, and the 

 silver pulverized very finelj. I also find it advantngeons to expose 

 the silvered alcohol to sun light one day. "When all dissolved, 

 filter tliesolution ; now decant ahout donl)le the quantity of hronn'zed 

 collodion wanted to use, and add to it a portion of the silvered 

 alcohol, in rpiantities not exceeding one or two drachms at a time, 

 and sliake well after each addition, until the silver is slightly in 

 C-xcess, which I ascertain hy pouring a small quantity of the collodion 

 into half an ounce of water, and shaking well, then, hy the addition 

 of a little salt, it will readily he seen if there is any free silver pres- 

 ent. If the silvei'ed alcohol is added in too large quantities at a time, 

 there will he a precipitate formed, which will require much shaking 

 to dissolve. In about one-half hour after tlie last quantity of silver 

 is added, the compound will he ready for use, hut will not keep good 

 in this condition more than three or four hours. As soon as the 

 plates are all coated, a quantity of the bromized collodion should l)e 

 added to the remaining portion of the sensitive compound; this addi- 

 tion will give it keeping qualities, in proportion to the amount of 

 bromized collodion added. If the bromized collodion is largely in 

 excess, it will keep several weeks, if not in excess, it will keep but a 

 few days. I develop with the alkaline developer. 



Prof. Tillman called attention to the propriety of some action upon 

 the matter of pliotographing the total eclipse of the sun on August 

 seventh. After discussion by several members, Mr. Mason olforod 

 the following motion : 



That the American Institute be requested to appropriate the sum 

 of five hundred dollars, to be expende<l under the direction of Lewis 

 M. Rutherford, in photographing the total eclipse of the sun on the 

 seventh of August next. The motion was seconded by I'rof. Till- 

 man, and unanimously carried. 



Mr. Boyle exhibited a drawing of his double field telescope, and 

 explained its advantages in use. 



Mr. Mason presented six stereographs of pathological specimens at 

 Bellevue Hospital. 



The Section then adjourned to the first Tuesday in Xovember. 



