Proceedings of the Polytechnic Asso>ciation. 823 



vibrations per second, it will be heard on the other locomotive at a 

 higher pitch than its real sound ; the diiFerence being due to the com- 

 bined speed of tlie locomotives, amounting to eighty-eight feet per 

 second. At the instant of passing the true tone is heard, and, as they 

 recede, the pitch will seem as much lower as it was before higher than 

 the true tone. The pitch will not descend below its first change, 

 because the locomotives are separating with a uniform speed. So, 

 likewise, a steamship sailing before the wind will not cross as many 

 waves as she does when going at the same speed against the wind. 



The change of pitch produced only by the very rapid movement 

 of the source of sound may be compared to the change of tint in the 

 spectrum of a heavenly body, as the result of its rapid motion to or 

 from the observer. It will, however, be borne in mind that, to detect 

 this change of tint, there must be a change of direction of the source 

 of light. This subject gave rise to an extended debate, in which Drs. 

 Parmelee, Kich, Bradley and others participated. 



Solid Exteact of Malt. 



W. A. Wetherby, M. D., introduced a new article of diet made 

 from malt, and after a brief reference to the forms of beverage 

 derived fi-om barley, and the objections to all of them, if taken, 

 under certain conditions, into the system, remarked that this " con- 

 centrated extract of malt" contained no alcohol, and, from tlie 

 peculiarity of its preparation, was incapable of undergoing the 

 vinous or acetic fermentation. Six ounces of this extract contains as 

 much nutriment as one-eighth of a bushel of the best malt. Mr. J. 

 G. Hovey, the representative of this new article, was then intro- 

 duced, who made still fuither explanation of its properties and uses. 



New Kekosene Lamp. 



An improved kerosene lamp, the invention of Mr. Hayden, of 

 Connecticut, was then exhibited. Its novelty consisted in having a 

 movable cup with perforated sides below the ring supporting the 

 glass, which could be slij^ped down the wick tube far enough to 

 allow the lamp to be filled, and the wick trimmed, without taking off 

 or moving the glass shade. A lady present objected to the plan, 

 because the bottom of the movable cup would soon be filled with 

 the crusts removed from the wick, and which could not be got out 

 without turning the lamp upside down. This difficulty the inventor 

 can doubtless obviate. 



