76 , SCIENTIFIC RECREATIONS. 



of steam, but the paper remains intact. It is well to perform this operation* 

 over a plate, in case of accident, as the water may be spilt. We may also 

 make use of an egg-shell as a little vessel in which to heat the water, by 

 resting it on a wire ring over the flame of the spirit lamp. 



Fig. 78 shows the arrangement of a very remarkable experiment, but 

 little known, on the refreezing of ice. A block of ice is placed on the edge 

 of jtwo iron chairs, and is encircled by a piece of wire, to which is suspended 

 the weight of say five pounds. The wire penetrates slowly, and in about an 

 hour's time has passed completely through the lump of ice, and the weight, 

 with the piece of wire, falls to the ground. What happens then to the block 



Fig. 78. Experiment on the regulation of ice. 



of ice? You imagine, doubtless, that it is cut in two. No such thing; it is intact,, 

 and in a single lump as it was previous to the experiment. In proportion 

 as the wire was sunk through the mass, the slit has been closed again by 

 refreezing. Ice or snow during the winter may serve for a number of experi- 

 ments relating to heat. If we wish to demonstrate the influence of colours 

 on radiation, we take two pieces of cloth of the same size, one white, and 

 the other black, and place them both on the snow, if possible, when there is 

 a gleam of sunlight. In a short time it will be found that the snow under- 

 neath the black cloth has melted to a much greater extent than that 

 beneath the white cloth, because black absorbs heat more than white, which, 

 on the contrary, has a tendency to reflect it. We perceive very plainly the 



