# Lectures on select subjects in mechanics, hydrostatics, pneumatics, and optics with the use of the globes, the art of dialing, and the calculation of the mean times of new and full moone and eclipses

### Popular passages

Page 96 - ... 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 71 - ... becaufe the weight of a column of water 33 feet high is equal to the weight of as thick a column of air, reaching from the furface of the earth to the top of the atmofphere...
Page 31 - ... 2. When the prop is at one end of the lever, the power at the other, and the weight between them ; 3.
Page 117 - ... and exhaust the receiver of air, and the pressure of the outward air on the surface of the quicksilver will force it through the pores of the hazel, from whence it will descend in a beautiful shower, into a glass cup placed under the receiver...
Page 60 - C is loose upon the shaft A, but is locked to the wheel B by the bolt Y. On this drum the great rope HH is wound ; one end of the rope being fixed to the drum, and the other to the follower G, to which it is conveyed over the pulleys / and K.
Page 145 - IK is formed but a little beyond it (with respect to the eye), as at n ; the consequence of which is, that the rays of the pencils will not be parallel after reflection from the small mirror...
Page 34 - 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 132 - 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 67 - The reason of this will appear from what has been already stated respecting the pressure of fluids of equal heights, without any regard to the quantities. For, if a hole be made in the upper board, and a tube be put into it, the water will rise in the tube to the same height that it does in the pipe ; and it would rise as high (by supplying the pipe) in as many tubes as the board would contain holes.
Page 60 - ... drag fidewife as they go along, and gives the load a much greater power of crushing them than when they are parallel to each other, but alfo endangers the over-turning of the carriage when any wheel falls into a hole or rut; or when the carriage goes...