716 Transactions of the American Institute. 



Decomposition and Recomposition of Light. 

 Mr. W. J. Lane used, in place of the costly apparatus generally 

 employed for this beautiful and instructive experiment, a glass tube 

 eight or ten inches long and half an inch in diameter, with a bore of 

 .05 to .09 of an inch. In a room containing only one light (a gas 

 flame, for instance), while standing a few feet from and facing it, 

 place the tube horizontally across the eyes and as near to them as 

 possible, and, on looking toward the light, a beautiful arc of large 

 size will appear, which is composed of a series of splendid spectra, 

 more or less brilliant, according to the refractive powers of the tube 

 and the distance of the observer from the light. Xow, upon revolving 

 the tube, while so placed, tlie arc of light will apparently revolve 

 very rapidly, the coloi's will be blended and ivJiiteW^xi produced; 

 thus affording a pleasing experiment. With large tubes of greater 

 dispensive power the effect would probably be more beautiful. 



Xew Aik Compressing Pump. 



Mr. Onofrio Abruzzo, late of Italy, exhibited his patent pump for 

 compressing air, described as consisting " in arranging a series of 

 vessels and providing each one with a pumping apparatus. When 

 the apparatus of the first pump is set in motion, it will compress the 

 air in all the vessels to a certain degree, according to the power of 

 the pumping apparatus and to the rapport between the two volumes 

 of air contained below the piston at the end of its upward and 

 downward strokes, which volume determines the compressing power 

 of the pumps. If the volume below the piston, when the same is at 

 its lowest stroke, is, for instance, the twentieth part of that volume 

 which is below the piston at the end of its upward stroke, the pump 

 will be able to compress twenty times the former volume at each stroke. 

 When all the vessels are filled with such compressed air, the apparatus 

 of the second vessel is set in motion and compresses the air in all the 

 vessels except tlie first." A brief discussion upon the merits of this 

 invention followed the inventor's explanation of its working. 



Dr. N. H. Barbour stated that he had constructed three pumps 

 similar to the one described, at the Morgan Iron Works in this city. 

 They are used for compressing carbonic acid gas, by which a pressure 

 of 1,500 pounds to the square incli can be obtained. 



Mr. C. E. Emory remarked that what is desirable in a good pump 

 is to have the space between the piston head and cylinder as small as 

 possible. The best pumps are made with the clearance between the 



