DISSOLVING VIEW INSTRUMENTS. 375 



&c., with several dozen slides, in a case, two feet long, 

 twenty inches wide, and fifteen deep a decided advan- 

 tage over every other description of dissolving-view ap- 

 paratus. 



The lamp is upon the ordinary fountain-lamp princi- 

 ple, with a circular wick like an argand burner, with a 

 small lime-hall suspended in the apex of the flame. In 

 the exact centre of the wick, and precisely level with the 

 top of it when raised, is a small tube for supplying oxygen 

 gas; at the bottom of this tube is a cup to receive any 

 overflow of oil, and underneath which is an elbow, ter- 

 minating with a union, where a flexible tube is united, 

 the other end being attached to a gas-bag filled with gas. 

 In trimming the lamp, care should be taken to cut the 

 cotton to a uniform height, to see that the edges form a 

 regular circle round the inner tube, without any portion 

 of the wick coming in contact with the oxygen tube ; and 

 the under part of the lime-ball should be suspended half 

 an inch from, and exactly over, the centre of the oxygen 

 tube. The wick of the lamp should not be raised too 

 high, but just to produce as much smoke as will be entire- 

 ly absorbed by the gas. Apply a pressure of about twen- 

 ty pounds on the bag, and sufficient gas only turned on 

 by the small stop-cock to produce perfect brightness. 

 This should be particularly attended to ; if too much gas 

 is turned on, the lime-ball is cooled, and gas wasted. The 

 advantages of this mode of illumination, and its applica- 

 bility to dissolving views, are : first, its intense brightness, 

 being of sufficient illuminating power, with condensers of 

 only three and three quarters inches diameter, to throw a 

 sharp and well-defined disc of twenty feet diameter; sec- 

 ondly, its maintaining a uniform brightness for two or 

 three hours consecutively, and, in this respect, superior 

 to the oxy-hydrogen light ; thirdly, the simplicity of ar- 

 rangement, and facility of management; fourthly, the 

 economy, the consumption of gas being very little more 

 than one cubic foot, and one ounce and a half of oil, per 

 hour. 



Directions for Use. The lantern should be placed from 

 twelve to fifteen feet from the screen, by which a disc of 

 these dimensions will be obtained ; and as the distance is 

 increased between the lantern and the screen, so in the 

 game ratio will the size of the disc be increased ; but if 



