1823.] Mr, Gray's Elements of Pharmacy, 459 



trial of it that it is adequate to its object, that of ascertaining 

 quickly and correctly the temperature at which dew begins to 

 be deposited. But we are not aware that in acconipHshing this, 

 it has any great advantage over ^he method of Le Koi, which is 

 recommended by the extreme simplicity of the apparatus 

 required. This consists of nothing more than a thermometer 

 and a glass tumbler filled with water, the temperature of which 

 is lowered by gradually adding ice (nitre or sal-ammoniac would 

 answer the same end) till dew begins to appear on the outer 

 surface of the vessel. Noting this point, whether obtained by 

 Le Roi's or Mr. Daniell's method, we then find, from Mr. Dal- 

 ton's table, the force of vapour at that temperature ; and from 

 the proportion which this force forms of the whole pressure of 

 the atmosphere at the time, we at once arrive at the absolute 

 quantity of vapour in a given space. We regard the indications 

 of this simple process as much more satisfactory than those of 

 Mr. Leslie's hygrometer, because, to deduce from the latter the 

 real proportion of vapour in air, requires a much more complex 

 calculation, of which some of the data, or of the steps, may pos- 

 sibly be erroneous. 



The remaining essays of Mr. Daniell we are obliged to pass 

 over without any notice. Indeed being chiefly composed of 



, details of facts, they are not from their nature susceptible of, 

 abridgment. They are important, however, to those who are 

 practically engaged in making or recording meteorological 



^ observations, and to all such persons, as well as to those who are 

 interested in the theory of atmospheric phenomena, we can 

 safely recommend the work as containing an ample fund of 

 valuable information. Z. 



The Elements of Pharmacy, and the Chemical History of the 

 Materia Medica, S^c. By Samuel Frederick Gray, Lecturer 

 on the Materia Medica, Botany, and Pharmaceutic Che- 

 mistry. 



It is impossible to deny 'that this work is calculated to con- 

 vey a considerable portion of information ; but it must at the 

 same time be admitted, that much of it will be of little use to the 

 student. The arrangement (if indeed arrangement it can be 

 called) is peculiar, and while some subjects are treated of with 

 extreme brevity, there are others which are extended much 

 beyond the requisite limits ; thus weights, measures, and 

 balances, occupy about 20 pages, furnaces 33, and the theory 

 of chemistry 34. The properties of atmospheric air and 

 water are then detailed; lead, copper, tin, and some other metals, 

 are next treated of in six pages ; and we are then surprised with 

 an account of the " alchemy of the Greek clergy," ** the intro- 

 - duction of alchemy into the west," and the " original theory of 

 transmutation ; " these disquisitions occupy about seven pages. 



