; the usual way of cutting off the steam is by means of a separate valve, termed an expansion valve; but such a device appears to be hardly necessary in ordinary engines.

"The upper valve is almost invariably wanting, though occasionally found in a perfect state of preservation in the white chalk at some distance.

Farcot, Edwards, and Lavagrian cut off the steam by the application of a supplementary valve at the back of the ordinary valve, which supplementary valve is moved by tappets fixed to the valve casing.

A, B, right pulmonary veins; with S, openings of the veins; E, D, C, aortic valves; R, aorta; P, pulmonary artery; O, pulmonic valves; H, mitral valve; K, columnæ carnoeæ; M, right ventricular cavity; N, interventricular septum.

The process of gastric digestion was studied many years ago by Dr. Beaumont and others, in the remarkable case of Alexis St. Martin, a French-Canadian, who met with a gun-shot wound which left a permanent opening into his stomach, guarded by a little valve of mucous membrane.

"Why," said the gentleman, "I used to apprehend such a catastrophe, but God has made a providential opening, a merciful safety valve, and now I do not feel alarmed in the prospect of what is coming.

This opening is guarded by the folds of the membrane forming the ileo-cæcal valve, which permits the passage of material from the small to the large intestine, but prevents its backward movement.

A, B, right pulmonary veins; with S, openings of the veins; E, D, C, aortic valves; R, aorta; P, pulmonary artery; O, pulmonic valves; H, mitral valve; K, columnæ carnoeæ; M, right ventricular cavity; N, interventricular septum.

A.And presses up and down the piston alternately, being admitted alternately above and below the piston by suitable valves provided for that purpose. 94.

When the handle H is pressed down, the levers in connexion with it open the upper exhausting valve E, and the lower steam valve V', and close the upper steam valve V and the lower exhausting valve E'.

Coming back from a spin down the lines we stopped in a small village called Amifontaine, to let our chauffeur, known affectionately as The Human Rabbit, tinker with a leaky tire valve or something.

On the top of this door is a small valve opening downward, called the atmospheric valve.

A cross head pump consists of a pump barrel, a plunger, one vertical check valve and two horizontal check valves, a globe valve and one stop cock, with more or less piping.

A cross head pump consists of a pump barrel, a plunger, one vertical check valve and two horizontal check valves, a globe valve and one stop cock, with more or less piping.

A weighted valve of safety valve pattern is attached to the air cylinder, and is connected with the air receiver, and with a discharge valve on each end of the air cylinder, also with a balanced throttle valve in the steam pipe.

Regulators may be divided into two sorts, viz., those with, sliding valves and steam ports, and those with conical valves and seats, of which the latter kind are the best.

In 1837 I employed, as an expansion valve, a rectangular throttle valve, accurately fitting a bored out seat, in which it might be made to revolve, though it did not revolve in working.

In the figure the piston is just about to commence its outstroke, the movement of the steam is supposed to be represented by the arrows; the inner steam valve s, and the outer exhaust e', are just beginning to open.

These stop valves are usually spindle valves of large size, and they are for the most part set in a pipe which runs across the steam chests, connecting the several boilers together.

A, B, right pulmonary veins; with S, openings of the veins; E, D, C, aortic valves; R, aorta; P, pulmonary artery; O, pulmonic valves; H, mitral valve; K, columnæ carnoeæ; M, right ventricular cavity; N, interventricular septum.

Pump valves for mines, &c. Punching and shearing boiler plates.

When the food, thoroughly mixed with saliva, reaches the stomach, the cardiac end of that organ is closed as well as the pyloric valve, and the muscular walls contract on the contents.

There were also queer valves, or tubes, in the helmet for letting out bad air, yet so contrived that no water could get in.

The stain of psychical pressure caused itthis explosion of unnatural laughter in both of us; it was an effort of repressed forces to seek relief; it was a temporary safety-valve.

Should the feed cock be shut so as to prevent any feed water from passing through it, the water will raise the topmost valve, which is loaded to a pressure considerably above the pressure of the steam, and escape into the hot well.