=Abraham, Heights of.= Near Quebec, Lower Canada. In the memorable engagement which took place here September 13, 1759, the French under Gen. Montcalm were defeated by the English under Gen. Wolfe, who was killed in the moment of victory. =Abri= (_Fr._). Shelter, cover, concealment; arm-sheds in a camp secure from rain, dust, etc.; place of security from the effect of shot, shells, or attack. =Absence, Leave of.= The permission which officers of the army obtain to absent themselves from duty. In the U. S. service an officer is entitled to 30 days’ leave in each year on full pay. This time he may permit to accumulate for a period not exceeding 4 years. An officer, however, may enjoy 5 months’ continuous leave on full pay, provided the fifth month of such leave is wholly distinct from the four-year period within and for which the 4 months’ absence with full pay was enjoyed. An officer on leave over this time is entitled to half-pay only. =Absent.= A term used in military returns in accounting for the deficiency of any given number of officers or soldiers, and is usually distinguished under two heads, viz.: _Absent with leave_, such as officers with permission, or enlisted men on furlough. _Absent without leave_; men who desert are sometimes reported _absent without leave_, to bring their crimes under cognizance of regimental, garrison, or field-officers’ courts; thus, under mitigating circumstances, trial by general court-martial is avoided. Absence without leave entails forfeiture of pay during such absence, unless it is excused as unavoidable. An officer absent without leave for three months may be dropped from the rolls of the army by the President, and is not eligible to reappointment. =Absolute Force of Gunpowder.= Is measured by the pressure it exerts on its environment when it exactly fills the space in which it is fired. Various attempts have been made to determine this force experimentally with widely different results. Robins estimated the pressure on the square inch at 1000 atmospheres, Hutton at 1800, and Count Rumford as high as 100,000 atmospheres. While Rodman, by experiments upon strong cast-iron shells, verified the accuracy of Rumford’s _formulas_, he found that his estimate of the force was greatly in error. According to Rodman the pressure is approximately 14,000 atmospheres. Dr. Woodbridge, another American philosopher and inventor, has shown that, fired in small quantities, the force of gunpowder does not exceed 6200 atmospheres. This agrees closely with the conclusion arrived at by the English “Committee on Explosives,” 1875, who found that even in large guns the force did not exceed 42 tons. =Absorokas.= A tribe of North American Indians. See CROWS. =Absterdam Projectile.= See PROJECTILE.