TRACT 35.

THE VIBRATING EPROUVETTE.

153

nearly in the proportion of their surfaces, or, which is thesame thing, as the squares of their diameters, being but verylittle higher, as might be expected. And this circumstanceis a proof both of the accuracy or regularity of the experi-ments themselves, and also of the theory of the resistances ofthe medium, in this instance.

TRACT

XXXV.

ON A NEW GUNPOWDER EPROUVETTE.

Art. 1. In the latter‘part of the preceding tract, it hasappeared that the eprouvette, which had been used, provedof very essential service to the success of the experimentsthere described ; so much so indeed, that, but for the use ofit, the object of the experiments would have been in a greatmeasure defeated, as no other known eprouvette could havebeen safely substituted for it, or have sufficiently answeredthe purpose in hand. It maj'' be important here to give adescription of the structure and use of this eprouvette,which may be of great and general benefit, wherever thequality of gunpowder is to be ascertained, as I know of noother machine by which that object can be effected, with somuch ease and certainty, and dispatch; the facility andquickness of execution being such, that the weighing theparcels of the powder is.the chief part of the operation ; andthe accuracy and uniformity are such, that a number of suc-cessive trials do not commonly differ by more than a smallfraction of a degree, out of an extent of 40 or 50 degreeson the instrument.