272 PHILOSOPHICAL TKANSACTIONS. [aNNO 1792. 



once for all. The process is not an approximation, but a plain arithmetical com- 

 putation, which may be carried on true to as many decimal places as the experi- 

 ments will allow. For this purpose indeed, it is necessary to have the weight of 

 a known measure of water. Mr. Ramsden's method of obtaining this, by means 

 of a cylinder, is far preferable to that of hollow cubes, particularly if the ends of 

 the cylinder can be made as true as the body of it. But in applying this instru- 

 ment to fix the term of proof, as proposed by that gentleman, it must be remem- 

 bered, that 7 lb. 13 oz. is not the weight of a gallon of proof spirit, but of spirit 

 1 to 6 under proof. On that proportion the value of proof was computed in 

 the report, by the same rule as Mr. Ramsden has since given, but which it was 

 not thought necessary to detail at full length. 



Though the quantity of extraneous substances, usually found in spirituous 

 liquors, does not increase their specific gravity so much as to be worth the con- 

 sideration of government, yet this is by no means tiie case when such substances 

 are added intentionally. The effect of alkalis is well known. Mr. Ramsden's 

 experiments show how great a change of specific gravity is produced by sugar, 

 when dissolved plentifully in weak liquors; and in an experiment made by order 

 of the Board of Excise, ^t pa'"t o( sugar, put into very strong spirit, reduced 

 its apparent strength no less than 17 per cent, by Clarke's hydrometer. 



I conclude with observing, that the execution of the experiments, and of the 

 computations, rested entirely with Mr. Gilpin, who is responsible for their accu- 

 racy, and entitled to the praise they may be found to merit. For the general 

 plan, as well as the particular methods adopted, I hold myself accountable, and 

 have now so fully stated my reasons for what I recommended to be done, that any 

 competent person will readily judge of their validity. In this and the foregoing 

 report, I have purposely avoided all philosophical deductions, and a comparison 

 with former experiments ; that the narrative might not be loaded with any foreio-n 

 matter, to interfere with the practical object for which this business was under- 

 taken. 



appendix to the foregoing Report. By Mr. George Gilpin, Clk, R.S. p. 439. 

 Having completed 2 instruments for trying the expansion of fluids, according 

 to the method described by Mr. Ramsden, with a stopper going into a tube on 

 the side of the ball, I now present an account of the experiments which I made 

 with them, that it may be judged how far such instruments are deserving of no- 

 tice. The scale of the longest admits of .26 of an inch for each degree of the 

 thermometer, and that of the shortest .17 of an inch for each degree. They 

 were charged with pure spirit: some of the same that was used in our experiments 

 by weight, specific gravity .82514: and having hung them up by the side of each 

 other to a piece of wood, provided for the purpose, with the same sensible ther- 



