Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 2, 1802).djvu/542

5 io] ICE place only during intense and sud- den frosts, in shallow waters,, the surfaces of which is disturbed either by the wind or the current of a stream, so that it cannot be easily consolidated. In many countries, the warmth of the climate renders ice not only a desirable, but even a necessary article : hence it becomes an ob- ject of some importance to procure it. in a cheap and easy manner. — • For this purpose, in the East In- dies, three or four pits are dug on a large open plain, each oi which is about thirty feet square, and two feet deep; the bottoms are covered, to the depth of eight or ten ir.cl.es with dried straw, or the stems of sugar-canes. On this bed are arranged, in rows, a num- ber of unglazed pans made of porous earth, about a quarter of an inch thick, and an inch and a quarter deep, which are. filled about sun-set, with water that has been boiled and become cool. — Early in the manning, a coat of ice is found on the pans, which is broken by striking an iron hook into its centre, and then conv yed in baskets to the place of preserva- tion. The most expeditious method, however, of producing ice, con- sists in a combination oi sal ammo- niac with nitre; h was first dis- covered by Boerhaave, whose experiments were repeated and confirmed by Mr. Walkejr, apo- thecary to the Radcliffe Infirmary, Oxford : but he found that his thermometer sunk 32° in a solu- tion of sal ammoniac, v. hen Boer- haave's fell only 2S° : i itre alcjne reduced it to ley. On mixing the two salts, in equal pr< poj tions,, the ■ r pi generating cold was con- siderably increased ; so that the ICE water was cooled to 22", wlrMe- the thermometer stood at 4/° in the op,-:n air. By adding some powder of the same composition, and immersing in the mixture two small phials filled with water, he found it in a short time frozen. Having observed that Glauber's salt, when it retains the water of crystallization, produces cold in a state of solution, Mr. Walker made an experiment of its effects when mixed witii the other salts before mentioned ; in consequence of which the thermometer sunk from 6g° to 19°, and he obtained ice, while the thermometer stood as high as JQ°. — Lastly, by pre- viously immersing the salts in the water of one mixture, and then making another of the cooled ma- terials, he was able to sink the mercury in the thermometer to 64°. Thus, he froze a mixture of. spirit of wine and water, in the proportion of seven of the latter to one of the former ; and, by adding a quantity of the cooled materials to the mixture in which this was frozen, the quick-silver fell to the extraordinary depth of (jcjdcgiees. . Various oilier methods of pro- curing artificial ice have, been con- trived, particularly by the aid of aether ; but that volatile spirit is too expensive for domestic pur- , and a satisfactory account of the process would exceed our limits. has lately also been intro- duced into medicine ; and its ex- ternal application was attended with success in various disorders, especially in typings lever, acute rheumatism, strangulated ruptures, and chrome inflanimakions of the eyes, aftenprpp r evacuations had preceded. It has likewise been advantageously employed for re- moving