274 Oti the ProdiiB'wn of aft'ifichl ColJ. 



made in the veflel B, and the vefiel covered by its lid D, then fet upright, and four dram* 

 of muriate of lime put into the cup b. 3d. A fimilar frigorific mixture is maJe in the 

 veflel A A, which is clofed with its lid C. 4th. This veflel being placed over the other, as 

 reprefented, three drams of water are tb be poured gently, through a funnel, into the tub? 

 a, and the aperture clofed. 5th. When the water is become perfedly folid ice,* the 

 grinding inftrument is to be put in, and, after fuff'ering it to remain a fliort tinie to be 

 cooled, the ice is. to be ground gently to fine powder, (an afliftant holding the apparatus 

 firm,) and.the inftrument contitiued quite through the aperture at the bottom of the tube. 

 6th. The whole of the ice-powder is then to be forced into the cup of the lower, veflel, and 

 ftirred about in it a little. 7th. The upper veflel being removed, and fet afide, the muriate 

 of lime and ice are to be thoroughly mixed, and a fmall tube, containing the quickfilver to h? 

 frozen, ftirred about in the mixture; or the bulb of a fpiiit-thermometer, to take its tem- 

 perature, which, if the experiment be conduced properly,, will indicate, even if the ex- 

 periment be made in fummer, a cold of — 50°. f 



The apparatus, as reprefented in the drawing, is upon as fit a fcale as may be required 

 for common experiments; by attention, however, to the proportions givenj one of any fize 

 may be procured. 



tliis purpofe, is that confifting of the fblution of three different falts in water ; and, in order to afcertam 

 what proportions may be ueceffkry to fill any CzeJ veffel, I (liali give the proportional quantities for a vefTel 

 containiug in nieafure a -ivi/ie pint, which are as follows : cf muriate of ammcnia 3 ounces, nitrate of pot- 

 afli 3 ounces, fulphate of foda 4 ounces ansl |, and water lOounces :. having procured the (alts I'epa.ately ift. 

 fine powder^ I put thefe firft into the veflt;!, ahd then fill up (without meafuring) the veflel with water. 



A mixture cf this kind, made in the fummer, when the temperature of the air is + 70", will cool th? 

 materials 10 + 20.°; and, if the falts and water are cooled to near + 50°, previoudy to mixing, by im- 

 merfion in cold water, to + 10°. My ui'uaJ method is, (wilhout taking the ufual precaution of cooling the 

 lalts,) to add the water much reduced in temperature, by punvping off a bucket or more firtt, by "which the 

 materials, confifting of muriate of lime and ice, are cooled to + \b* before mixing. 



In winter, the experiment may be conduced by adding fnow, at the temperature. of the air, to muriate of 

 lime, (cooled to a low temperature,) in the veffel B. In fummer, by adding ice-powder, cooled to a low 

 temperature, in the veffel A, to muriate of lime cooled to + 50°, by water, (inftead of a frigorific mixture,), 

 in the vtffel B. 



The temperature of the fprings, or of well-water, it is well known, is in this climate nearly 4- 50' 

 throughout the year. 



* At this period, I /hake the apparatus, in order to expedite the folution of the falts, and to diffule the 

 effefts of the freezing mixtures ; or, ifneceffary, reneiAi ihtm. 



t Muriate of lime and ice-powder, mixed at the temperature of -f 20°, give a cold of— 48° ; if mixed 

 :\t-J- 15, of — 51°j and, at + 10°,. a coldof — 54'». 



The freezing point of quickfilver is — 39° ; but that metal requires a temperature of — 45°, to affume its 

 perfeilly folid ftate. 



I have repeatedly frozen quickfilver in the middle of fummer, by mixing together muriate, of lime and ice- 

 powder, at + 20° i and likcwife, by mixing together nitrous acid and ice-powder, at + S*. 



Muriate 



