684 PHILOSOPHICAL TRANSACTIONS. [aNNO l/QO. 



From this table, when the specific gravity of any spirituous liquor is ascer- 

 tained, it will be easy to find the quantity of rectified spirit, of the above-men- 

 tioned standard, contained in any given quantity of it, either by weight or mea- 

 sure. As common arithmetic is competent to furnish the rules for this purpose, 

 it would be superfluous to give them here. All the objects of inquiry relative 

 to this business should. Dr. B. thinks, be reduced to tables ; the first of which 

 might exhibit the specific gravities of different mixtures, from 1 to 100 parts of 

 water, increasing by 1, at every degree of heat from 40 to 80, being the utmost 

 limits of temperature that can be wanted in common practice. This table need 

 only be calculated to 3 places of figures, which will always give the quantity of 

 spirit true within a 50th part of the whole, and in the most usual degrees of 

 heat within a 100th ; and to this number of figures the areometer, or hydro- 

 meter, showing the specific gravities, could be suited. A further reason for 

 continuing only to 3 places of figures is, that, accurate as Mr. Gilpin's experi- 

 ments have been, some irregularities are found in the last 2 of the 5 decimals 

 to which his tables are calculated. The greatest of these irregularities do not 

 exceed the quantity corresponding to a difference of -^ of a degree of heat, and 

 in general they are much less. A table might be constructed to show what the 

 numbers would probably have been, to the 5 places of decimals, if there had 

 been no kind of error in the experiments. — Another table should be of the vo- 

 lumes, exhibiting what proportion the spirit and water bore to each other by 

 measure or bulk, in the different mixtures ; whence might be calculated a very 

 useful table of diminutions, to show when a given weight, or volume, of a 

 certain spirit and water are mixed together, how much their bulk would be di- 

 minished ; or, what is called by the distillers the concentration. From such a 

 table the distiller could learn what quantity of water he must mix with spirit of 

 a given strength, in order to reduce it to proof spirit, or any other strength j 

 and also what quantity of proof spirit, or spirit of any other strength, he may 

 obtain, by adding water to spirit of a given strength ; both circumstances very 

 necessary to be known in the trade, and which some of the sliding rulers now 

 in use profess to point out. 



It may appear odd, that no mention has been made till now of proof spirit, 

 the standard to which most of the regulations of the excise have hitherto been 

 referred. The reasons for not adopting this standard are : first, that the strength 

 of spirit to be called proof is a mere arbitrary point, and by no means so 

 exactly determined as could be wished ; and 2dly, that it seemed most convenient 

 to take for the standard the highest strength of spirit usually found in com- 

 merce, and beyond which it cannot be rectified without a process of some ex- 

 pense, so that all the other degrees of strength might be reckoned one way, 

 without the intervention of a middle point, inducing the necessity of denomi- 



