822 Transactions of the American Institute. 



odor, and condensing npon the chimney and outside of the lamp, was 

 completely avoided. For the same reasons the chimneys are less 

 liable to break. The combustion being more perfect, less oil is used. 

 The invention did not draw forth much discussion. 



Effects of Salt Water on a Surface Condenser. 



Mr. Charles E, Emery exhibited seamless tubes from a surface con- 

 denser in which the salt water of the harbor was used to cool the 

 tubes containing steam. The tubes were eaten through in many 

 places, yet the same kind of tubes are used on ocean steamers, and 

 such tubes are not thus affected. The cause was ascribed to chemical 

 action. 



Adjourned. 



October 15, 1868. 



Professor Samuel D. Tillman in the chair ; Mr. C. E. Emeky, Secretary. 



The Spectroscope in Astronomy. 



Dr. Yanderweyde spoke at length on the use of the spectroscope 

 in astronominal observations. The first part of his discourse was 

 devoted to an exposition of the received vibratory theory of light, 

 and the analogy between liglit and sound as the results of vibrations, 

 lie tlien described the method by which Iluggins, of England, was 

 enabled, with the spectroscope, to decide whether certain fixed stars 

 were in reality fixed as regards their distance from the solar system. 

 If they approach or recede there must be a change in the colors of 

 their spectre, resulting from a difierence in the number of waves 

 producing light which reach us. This point is well illustrated by a 

 change in the pitch of a note coming from a body in motion. Most 

 persons have observed, while riding in a railway train, tliat the 

 sound of the whistle of the locomotive on a train passing by in 

 an opposite direction seems of lower pitch while receding than 

 when approaching. This is accounted for by the fact that to pro- 

 duce a note of a given pitch, a given number of air waves must 

 strike the ear in a given time. If the number of waves is increased, 

 there is a rise in tlie pitch; if decreased, there is a fall. Sound 

 travels at the rate of about 1,120 feet in a second, a change in the 

 temperature of the air of course altering that rate. If two loco- 

 motives are approaching each other, each at tlie rate of thirty miles 

 per hour, and the whistle on one sounds the note C, made by 522 



