50 Notices respecting Neiv Books. 



This instrument consequently does not require the aid of any com- 

 putation, but is simply filled with the fluid to be examined, and placed 

 in one scale of the balance, while its counterpoise is placed in the 

 other. If the contained fluid be lighter than water, it will appear 

 deficient in weight, and as many grains must be added to the scale 

 that contains it as may be sufficient to restore the balance. This 

 shows at once that the specific gravity of the fluid in question is ne- 

 gative, or less than the standard (1000), and consequently that it 

 must be expressed by a fractional number; but, should the fluid be 

 heavier than water, the bottle will preponderate, and weights must be 

 put in the opposite scale, when their amount being positive, must be 

 added to that of the standard. For example, if the bottle were filled 

 with sulphuric sether, it would require from its being lighter than 

 distilled water 739 grains to be placed in the same scale to restore 

 the balance, and consequently its specific gravity would be expressed 

 thus, 0-739." 



Now we will grant that this is the true specific gravity of the fluid 

 in question : but Dr. Graham has committed the extraordinary blunder 

 of deducting 739 from 1000, and finding that 739 remain ; the real 

 fact being that only 261 grains should be put into the scale with the 

 bottle, which would indeed give 0739 as the specific gravity of the 

 fluid. 



Dr. Graham then proceeds thus : — " Had it (the thousand grain 

 bottle) been filled with sea-water, which is rather more dense than 

 that which is distilled, twenty-six hundredths, or rather better than 

 a quarter of a grain, must have been added in the opposite scale, and 

 which, as already explained, must be added to the standard 1-000 to 

 express the specific gravity of such water, which would be stated thus, 

 1-026." 



We will again admit Dr. Graham's accuracy in stating the specific 

 gravity of the fluid under consideration, but there must be some pe- 

 culiarity in his edition of Cocker ; for it would seem to show that by 

 adding twenty-six hundredths of a grain to 1000 grains, they become 

 one thousand and twenty-six grains. If this be one of "the recent 

 discoveries in science" to which Dr. Graham alludes in his title page, 

 it is not, we venture to pronounce, one of those which it is the boast 

 of the author to have " clearly and fully explained." 



Agiiin ; in illustrating the method of taking specific gravities, — an 

 operation which we are sure Dr. Graham never performed,^ — he sup- 

 poses that he takes a piece of gold, weighing 48 grains, which he 

 further supposes to lose 6 grains by immersion in water; he then adds 

 " we now divide the real weight of the body in air, viz. 48 grains, by 

 this loss, 6 grains ; which gives us 8 as the specific gravity of the 

 body under examination." Now this is really something new, viz. 

 that the specific gravity of gold is only 8 ; and what is truly astonish- 

 ing, is, that Dr. Graham has so entirely forgotten to take advantage 

 of his own discovery, that in p. 307 of the Catechism, we actually 

 find him recurring to his usual practice, and stating the specific gra- 

 vity of gold to be 19-30, which he learned from one of the authors 

 whom he has laid so largely under contribution. 



Dr. 



