284 SCIENTIFIC AMUSEMENTS. 



Ked heat just visible in diffused daylight, . 500 to 550 



Full red heat (cherry red), ... . 700 to 800 



Melting point of silver, .... . near 1000 



Intensely white heat, .... 1300 to 1500 



Melting point of platinum, ... . near 2000 



Expt. 329. To show that Bodies differ in their Capacities for 

 Heat. Into three similar basins or dishes put exactly equal 

 quantities of water measured in a graduated vessel ; say half a pint 

 = 10 ounces in each ; if the water have been taken out of the same 

 jug, obviously each one of the three quantities will have the same 

 temperature to begin with, which equality of temperature may be 

 readily proved by means of a thermometer. 



Provide a lump of lead weighing say 4 ounces, and tie a string 

 to it, so that it can be lowered into a saucepan full of boiling 

 water ; when it has got hot (after some three or four minutes), lift 

 it out by the string and quickly plunge it into one of the basins of 

 water ; stir up this water for two or three minutes, and take its 

 temperature by means of the thermometer ; of course the water 

 will have become a little hotter through plunging the hot lead 

 into it; if the original temperature were, say 15 C., the 

 temperature after the hot lead was plunged in will rise to some- 

 thing like 16, or a little higher. Now repeat the experiment, 

 using instead of the lead a lump of tin of exactly the same weight 

 as the lead, and plunging the hot tin into the second basin ; the 

 thermometer in this case will rise considerably more, say from 15 

 to about 17, showing that the tin at the temperature of boil- 

 ing water parts with more heat in cooling down than does the 

 lead ; whence evidently more heat would be required to heat up 

 the tin than the lead, i.e., the tin has a greater capacity for heat 

 than the lead roughly speaking, about twice as much the rise in 

 temperature of the water in the basin being nearly twice as great 

 with the tin as with the lead. 



Into the third basin plunge similarly a lump of iron of the same 

 weight as the lead or tin previously used, and similarly heated in 

 boiling water ; the rise in temperature of the water due to the heat 

 parted with by the hot metal in cooling will now be greater still, 

 amounting to about 4 showing that the capacity for heat of 

 iron is nearly twice as great as that of tin, or four times as great as 

 that of lead. 



If a piece of aluminium of the same weight as before were used, 

 the rise in temperature of the water would be again nearly doubled, 

 since the capacity for heat of aluminium is nearly double that of 

 iron, quadruple that of tin, and about 8 times that of lead ; whilst, 

 if instead of a piece of hot metal an equal weight of boiling water 



