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THE POPULAR SCIENCE MONTHLY. 



of tin are fastened to the top of the tube and to the inner rim, as 

 shown in the woodcut, where the middle strip conceals the central 

 tube. There is room inside the circle of test-bottles to place the other 

 bits of apparatus when not in use. The whole construction occupies 

 but a small space, and can be conveniently set aside when not required, 



Rains's Revolving Test-Stand. 



or left in any corner or closet, and covered by a piece of cloth, to pro- 

 tect it from dust. For practice it is placed on any common table, 

 and two pupils can readily use it at the same time from opposite sides. 

 It turns so easily that any test-bottle wanted can be taken and directly 

 returned to its numbered place, so that it is kept constantly in order 

 for continued exercises. 



It must not be supposed that this is merely a nice plaything to ena- 

 ble boys and girls to make amusing chemical experiments. Professor 

 Rains had a very serious purpose in preparing it ; and it is designed 

 for systematic chemical work. It has been adapted to take pupils 

 through a course of qualitative chemical analysis. Besides the neces- 

 sary apparatus, there is a sufficient equipment of test-substances for 



