580 PHILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



As soon as this discovery came to my knowledge, on the 23d of February, a 

 thaw having begun 3 days before, after a frost which had continued with very 

 little intermission from the 24th of December, I collected a quantity of ice, and 

 stored it up in a large cask in a cellar. I thought it necessary to satisfy myself in 

 the first place, by actual experiment, that ice, how cold soever it may be, comes 

 up to the freezing point through its whole mass before it begins to liquefy on 

 the surface. For this purpose I cooled a large fragment of ice, by a freezing 

 mixture, to 17° of Fahrenheit's thermometer, and then hung it up in a room 

 whose temperature was 50°. When it began to drop, it was broken, and some 

 of the internal part quickly pounded and applied to the bulb of a thermometer 

 that was cooled by a freezing mixture below 30°. The thermometer rose to, 

 and continued at 32°; being then taken out, and raised by warmth to 40°, some 

 more of the same ice, applied as before to the bulb, sunk it again to 32°; so that 

 no doubt could remain on this subject. 



Apprehensive that pounded ice, directed by the authors, might imbibe and 

 retain more or less of the water by capillary attraction, according to circumstances, 

 and thus occasion some error in the results, I thought it necessary to satisfy my- 

 self in this respect also by experiment. I therefore pounded some ice, and laid 

 it in a conical heap on a plate; and having at hand some water, coloured with 

 cochineal, I poured it gently into the plate, at some distance from the heap; as 

 soon as it came in contact with the ice, it rose hastily up to the top, and on 

 lifting up the lump, I found that it held the water, so taken up, as a sponge 

 does, and did not drop any part of it till the heat of my hand, as I suppose, be- 

 gan to liquefy the mass. On further trials I found, that in pounded ice pressed 

 into a conical heap, the coloured water rose, in the space of 3 minutes to the 

 height of 2-i- inches; and by weighing the water employed, and what remained 

 on the plate unabsorbed, it appeared, that 4 ounces of ice had thus taken up, 

 and retained, 1 ounce of water. 



To further ascertain this absorbing power, in different circumstances, more 

 analogous to those of the process itself, I pressed 6 oz. of pounded ice pretty 

 hard into the funnel, having first introduced a wooden core in order to leave a 

 proper cavity in the middle: then, taking out the core, and pouring 1 oz. of 

 water on the ice, I left the whole for half an hour; at the end of which time 

 the quantity that ran off was only 12 pennyweights and 4 grains, so that the ice 

 had retained 7 pennyweights and 20 grains, which is nearly -J^- of its own weight, 

 and f of the weight of the water. 



These previous trials determined me, instead of using pounded ice, to fill a 

 proper vessel with a solid mass of ice, by means of a freezing mixture, as the 

 frost was now gone, and then expose it to the atmosphere till the surface began 

 to liquefy. The apparatus I fitted up for this purpose was made of earthen-ware 



