644 , PHILOSOPHICAL TRANSACTIONS. [aNNO 1775. 



These are unglazed, scarcely a quarter of an inch thick, about an inch and a. 

 quarter in depth, and made of an earth so porous, that it was visible, from the 

 exterior part of the pans, the water had penetrated the whole substance. 

 Towards the dusk of the evening, they were filled with soft water, which had 

 been boiled, and then left in the beforementioned situation. The ice makers 

 attended the pits usually before the sun was above the horizon, and collected in 

 baskets what was frozen, by pouring the whole contents of the pans into them, 

 and thus retaining the ice, which was daily conveyed to the grand receptacle or 

 place of preservation, prepared generally on some high dry situation, by sinking 

 a pit of 14 or 15 feet deep, lined first with straw, and then with a coarse kind 

 of blanketing, where it was beaten down with rammers, till at length its own 

 accumulated cold again freezes and forms one solid mass. The mouth of the 

 pit is well secured from the exterior air with straw and blankets, in the manner 

 of the lining, and a thatched roof is thrown over the whole. 



The quantity of ice depends much on the weather ; so that it has sometimes 

 happened, that no congelation took place. At others perhaps half the quantity 

 will be frozen ; and often the whole contents are formed into a perfect cake of 

 ice : the lighter the atmosphere, and the more clear and serene the weather, the 

 more favourable for congelation, as a frequent change of winds and clouds are 

 certain preventives. For it is frequently remarked, that after a very sharp cpld 

 night, to the feel of the human body, scarcely any ice has been formed ; when 

 at other times the night has been calm and serene, and sensibly warmer, yet the 

 contents of the pans will be frozen through. The strongest proof of the in- 

 fluence of the weather appears by the water in one pit being more congealed 

 than the same preparation for freezing will be in other situations, a mile or more 

 distant. 



The climate may probably contribute in some measure to facilitate the conge- 

 lation of water, when placed in a situation free from the heat of the earth, 

 since those nights in which the greatest quantity of ice has been produced, were, 

 as before observed, perfectly serene, the atmosphere sharp and thin, with very 

 little dew after midnight. The spongy nature of the sugar-canes, or stems of 

 the Indian corn, appears well calculated to give a passage under the pans to the 

 cold air ; which, acting on the exterior parts of the vessels, may carry off by 

 evaporation a part of the heat. The porous substance of the vessels seems 

 equally well qualified for the admission of the cold air internally ; and their 

 situation being full a foot beneath the plane of the ground, prevents the surface 

 of the water from being ruffled by any small current of air, and thus preserves 

 the congealed particles from disunion. Boiling the water is esteemed a necessary 

 preparative to this method of congelation ; but how far this may be consonant 

 with philosophical reasoning, Sir R. presumes not to deternjine. 



