TRACT 37.

OF GUNNERY".

315

log. of ~), where a and b are expressed in calibers of the.gun, as they stand in the first and second columns of thelast table. So that this table and the rules are general forall calibers or diameters of guns, as well as all lengths ; andfrom which the practical artillerist may derive the greatestadvantage. If he wish to know what may be the best chargefor any gun he wants to employ, knowing only how manycalibers it is in length, with the weight of the ball; by look-,ing in the table, he sees at once both the length of the chargeof powder, and its weight, as well as the degree of velocityit will communicate. If the length, in any case, fail betweenany two adjacent numbers in the first column, it is then onlynecessary to take the like medium between the correspond-ent numbers in the columns of powder and velocity. If a lessdegree of velocity be necessary, the correspondent charge ofpowder may be found, by taking it in proportion to thesquare of the velocity ; viz, by saying, as the square of thetabular velocity is to the tabular charge of powder, so is thesquare of the proposed velocity, to the charge desired : andthus in many cases a needless waste of powder and velocitymay be prevented. In fine, it may be with truth remarkedthat this table, and the foregoing rules, being deduced fromvery numerous and laborious experiments, may be dependedon for practice, as far more exact and satisfactory than any-thing of the kind that has been before given for such pur-poses.