266 



SCIENTIFIC AMUSEMENTS. 



that the spiral uncoils ; conversely, on cooling the spiral twists up 

 closer. The upper end of the spiral is fixed to a firm support, S ; to 

 the lower end a long index is attached, so that the temperature is 

 read off by the position of the index on a circular scale, somewhat 

 like the hand of a watch on the dial. 



Expt. 314. To show that Liquids do not all Expand alike. 

 A series of bulbs of equal size blown on tubes of the same bore 

 are arranged side by side (fig. 121) with the bulbs in a trough, 

 so that they can all be heated simultaneously to the same extent 



by pouring warm water into 

 the trough. The bulbs and 

 tubes are first filled to con- 

 venient heights with differ- 

 ent fluids (alcohol, water, 

 benzene, oil of turpentine, 

 ether, &c.), the levels being 

 read off on scales fixed for 

 the purpose. On heating 

 the bulbs in the trough, the 

 different liquids will be 

 found to ascend in the tubes 

 to very different extents. 

 Thus, water expands much 

 less than alcohol for a 

 Fig. 121. Expansion of Liquids. g i ven r i se o f temperature, 



whilst benzene expands more than alcohol, and ether more still. 

 Instead of purchasing bulbs and tubes, the apparatus may be readily 

 constructed at home by selecting a number of small flasks all of as 

 nearly as possible the same size (best ascertained by measuring the 

 quantity of water that each will hold), and fitting them with per- 

 forated corks and pieces of quill tubing of the same bore for each. 



Expt. 315. Irregular Expansion of Water. A remarkable 

 peculiarity in the expansion by heat is exhibited by some few 

 substances, and more especially by water and bismuth. If a block 

 of ice be melted so as to form water at 0, and this water be 

 allowed to rise in temperature, it will be found to shrink in volume 

 until the temperature reaches about 4 C., after which it begins to 

 expand as the temperature rises. In consequence, a given quantity 

 of water occupies the least possible space at 4 ; or otherwise, a 

 given space filled with water will hold a larger weight of water 

 at 4 than at any other temperature. Accordingly 4 is spoken 

 of as the temperature of maximum density of ivater. 



A bucket of water in a cold room during frosty weather fur- 

 nished with two thermometers, one indicating the temperature of 



