582 Transactions of the American Institute. 



appears, is a tolerable length of time compared with that in which 

 photographs are taken by the electric flash. The duration of the 

 illuminating sparks, according to the beautiful and trustworthy 

 experiments of Mr. Wheatstone with his delicate chronoscope, does 

 not exceed the millionth part of a second, and yet a clear and dis- 

 tinct photographic image is obtained by a single electric discharge. 

 By this means may be shown the real form of objects to which a 

 deceptive appearance is given by their rapid movement. If a wheel 

 on whose side any figure is drawn in conspicuous lines be made to 

 rotate with the greatest possible velocity, the figure will present to 

 the eye only a series of concentric bands of different shades. Let it 

 now be photographed while in motion by the electric flash, and the 

 wheel will appear stationary with the figure well defined. A vein 

 of water issuing from a small orifice, which appears to the eye as 

 smooth as a stem of crystal, if seen or photographed by the light of 

 the electric discharge, is shown to be composed of drops variously 

 disposed, and of various forms, some being elongated, others flattened, 

 and others almost spherical. 



Mr. Fisher suggested that perhaps photography might aid in 

 determining the speed of light. 



Y. The Gasophaner. 

 An invention that may develop into something of great value is 

 that of an English chemist, designed to show the existence of mala- 

 rious gases. A piece of fused boracic acid, the size of a walnut, is 

 heated to redness in chlorine. The mass is then blown the same as 

 common glass into a bulb, and the "gasophaner" is ready for use. 

 "When first made the bulb is perfectly clear, but in being brought 

 into contact with carbonic acid gas it becomes clouded with a light 

 blue film, giving an opal luster. By gentle reheating the film passes 

 away. So great is the delicacy of the gasophaner that the breath 

 of a child or a healthy person, breathed on the bulb, can be detected 

 from that of a person exhaling more carbonic acid. When held over 

 a solution of sulphur the bulb becomes pitted as with small-pox. 



Emery. 

 The President said — A new vein of emery has been discovered 

 quite recently, specimens of which will be presented by Mr. Stewart, 

 who owns the land on which it is located. Powdered emery is used 

 in large quantities for scouring, smoothing and polishing hard sub- 

 stances. The mineral is chiefly brought from Naxos and points still 



