46 HEAT OR CALORIC. 



Let two globular glass vessels, with long narrow necks, as nearly 

 as possible of the same size and shape, be supplied severally, with 

 water and alcohol, excepting the necks from N N to O O. Under 

 each vessel, place equal quantities of charcoal, burning with a similar 

 degree of intensity. The liquids in both vessels will be expanded, 

 so as to rise into the necks ; but the alcohol will rise higher than the 

 water. Hare. 



(c.) A retort of glass inverted with its mouth in a colored fluid 

 gives out air, if the ball be heated ; and if the heat be 

 withdrawn, the column of fluid ascends and occupies the 

 place of the air that was expelled. A heated ladle an- 

 swers well to hold over the bulb of the retort. 



The experiment will be more striking if the retort has 

 a very long and narrow neck, or if a tube be inserted in 

 the mouth to elongate the neck. 



A moist flaccid bladder with the neck tied, is swollen by 

 the application of heat, and bursts if the heat be great ; 

 it is of course contracted when the heat is withdrawn. 

 In this experiment, hot water is a good medium for the expansion, 

 and cold water for the contraction. 



(flf.) The pyrometers described in the books of natural philosophy 

 demonstrate the expansion of solids with great delicacy.* 



An excellent pyrometer has been executed by Mr. Terry, of Salem, 

 Connecticut. A small iron cylinder is heated by a long thin wick 

 fed by alcohol, contained in a horizontal slitted tube, and by means of 

 levers and multiplying wheels, the motion is so increased, that an in- 

 dex moves rapidly over a graduated circle, and the opposite motion 

 takes place when the cylinder is cooled. Any other metal may be 

 substituted. One of these instruments is in the laboratory of Yale 

 -College. We subjoin a figure of a similar pyrometer used by Dr. 

 Hare. 



* See Webster's Manual, p. 23 ; Ann. de Chim. et de Phys. V. 312, Breguet ; 

 and Journal of Science, XI. 809, Daniel, and especially the Library of Useful 

 Knowledge, Art. Pyrometer. 



