# Lectures on Select Subjects in Mechanics, Hydrostatics, Hydraulics, Pneumatics, and Optics: With the Use of the Globes, the Art of Dialing, and the Calculation of the Mean Times of New and Full Moons and Eclipses

W. Strahan, 1776 - Astronomy - 444 pages

### Popular passages

Page 157 - ... once what is the weight of a quantity of water, equal in bulk to the solid matter in the sand ; and by comparing this with the weight of the sand, we have its true specific gravity.
Page 68 - ... 152 times as great as the distance between the spirals : and therefore a power at the handle, whose intensity is equal to no more than a .single pound, will balance 152 pounds...
Page 108 - ... up the board with all the weights upon it •, and if the pipe be kept full, until the weights are raifed as high as the leather which covers the bellows will allow them, the water will remain in the pipe, and fupport all the weights, even though it...
Page 197 - Set a lighted candle upon the pump, and cover it with a tall receiver. If the receiver holds a gallon, the candle will burn a minute ; and, then, after having gradually decayed from the first...
Page 110 - K : and then the leaden bottom EFG will be plunged to the depth of fomewhat more than eleven times its own thicknefs : holding the tube at that depth, you may let go the thread at L, and the lead will not fall from the tube, but will be kept to it by the upward...
Page 182 - ... in the frame. Each mill has four thin arms or sails, fixed into the axis : those of the mill a have their planes at right angles to its axis, and those of...
Page 49 - ... 2. When the prop is at one end of the lever, the power at the other, and the weight between them.
Page 214 - But that vision is effected in this manner may be demonstrated experimentally. Take a bullock's eye while it is fresh, and having cut off the three coats from the back part, quite to the vitreous humour, put a piece of white paper over that part and hold the eye towards any bright object, and you will see an inverted picture of the object upon the paper. Since the image is inverted, many have wondered why the object appears upright. But we are to consider, 1. That inverted is only a relative term;...
Page 54 - To this sort of lever are generally referred the bones of a man's arm ; for when he lifts a weight by the hand, the muscle that exerts its force to raise that weight is fixed to the bone about one tenth part as far below the elbow as the hand is. And the elbow being the centre round which the lower part of the arm turns, the muscle must therefore exert a force ten times as great as the weight that is raised.
Page 189 - Take a receiver, having a brass cap fitted to the top with a hole in it; fit one end of a dry hazel branch, about an inch long, tight into the hole, and the other end tight into a hole quite through the bottom of a small wooden cup ; then pour...