Jjgg PHILOSOPHICAL TRANSACTIONS. [aNNO 1747. 



formed such variety of useful instruments, but likewise cookery, which is so 

 much concerned about the food of mankind during health, and also pharmacy, 

 which furnishes medicines for restoring health when lost, the art of dying, and 

 many other useful manufactures, all owe their improvements to this science ; 

 many of which have occurred unexpectedly to the operator while he had some- 

 thing else in view : but in many cases the chemists complain, that, having once 

 accidentally hit on a curious experiment, on endeavouring to repeat it, they have 

 never been able to make their process succeed exactly, as it did the first time, 

 though they made use of the same materials, in the same quantity, and con- 

 ducted the process through exactly the same operations. Where then must the 

 cause of the miscarriage lie? Surely in the degree of heat made use of in the two 

 experiments; for in many common operations, how usual is it for a preparation 

 to be spoiled either by too little, or most commonly by too much fire, too long 

 or too short a time applied ! In order therefore to prevent these many miscar- 

 riages, Dr. M. advises the chemist, in his operations, to observe his clock with as 

 much exactness as the astronomer does in his observations ; and in order to know 

 to a certainty the very degrees of heat he ever made use of in any process, that 

 so he may be able to repeat and continue the same again in any repetitions of 

 the same experiment. Let him have his laboratory furnished with various kinds 

 of thermometers, proportioned to the degree of heat he intends to make use 

 of He will find these instruments as useful to him in his processes, as they 

 have proved to the curious gardener in his stoves, who by them is taught to 

 keep his plants in the same degrees of heat as are natural to them in their re 

 gpective climates; which has been set forth in tables, after a very ingenious 

 manner, by Mr. Sheldrake of Norwich. And besides enabling him to perform 

 his operations with more exactness, these instruments would save him a great 

 deal of fuel ; for as liquors while boiling are not capable of receiving a greater 

 degree of heat, all fuel which is used more than to keep them in that state, is 

 useless ; and the like happens in many other cases. 



These instruments would also be of great service to maltsters, brewers, distil- 

 lers, and vinegar-makers; for, by thermometers placed in different parts of the 

 heap of wetted malt, the proper heat for its sprouting might be determined, 

 and then regulated: the same for the heat of the kiln when the malt is spread on 

 it. By thermometers the brewer may ascertain the heat of the water when he 

 pours it on the malt, the heat of the wort when he sets it to work, and the heat 

 while working: and in like manner the distiller and vinegar-maker, in short, 

 every artificer who employs heat in his business, may by these instruments be 

 certain of every degree necessary in each part of his work. 



Many experiments show that all known bodies, whether fluid or solid, increase 

 their bulk, or rarefy, by an addition of heat; and on the contrary, contract or 



