become of great use to mankind, particularly for raising water, which shows the number of lbs. which may be raised 1,800 times per hour, to a height of six inches, by cylinders half-filled with water, as well as the different diameters and depths of the said cylinders."

There is no improvement here upon the plan of the Marquis of Worcester; but it is worthy of note how near the calculations of Sir Samuel Morland were, as to the amount of expansion that water would undergo in its conversion into steam-said to be 2,000 times-the actual expansion being abont 1,700 times.

Evelyn describes an interview he had with Morland, in 1695, and though he was then blind, he still found him surrounded by his mechanical inventions. This shows "the ruling passion strong in death," and proves that this great man was a real genius. He died in January, 1696. It is worthy of note, that the whole effective agency of steam, as a motive power, depends upon the principle here propounded by Sir Samuel Morland, namely, its expansive nature; and for the information of the students of this Institution, I may say that one cubic inch of water converted into steam will form a cubic foot of elastic vapour, and, of course, in proportion to the pressure at which this vapour is used, will depend its results. Water, as you all know, is converted into steam at 212° heat; but it is found that steam is more effective if used at a temperature of from 250° to 300°, as it is thus cleared of those particles of watery vapours with which steam is generally charged when first evaporated in the boiler, and which, combined with the steam, considerably retards its effective power. When steam is in a perfectly pure and healthy condition, it is quite dry, and will not even make damp a silk pockethandkerchief, if placed in the steam-pipe. At the same time, it ought to be stated that, if steam is heated much above 300° of temperature, it loses its power; for, in that case, it becomes absorbed and lost as caloric. After this digression, we will now continue our history of the Steam Engine, and the next hero who claims our notice is

DR. DENNIS PAPIN (A.D. 1690).

Dr. Papin was a native of Blois, in France, and was the first to suggest the idea of a piston working in a cylinder. The idea seems never to have been carried out; but still

great credit is due to Dr. Papin for the idea. His plan was to have a piston floating in a cylinder partly filled with water, and, by the application of heat, to convert the water into steam, and thus raise the piston; then to produce a vacuum by the removal of the heat, and allowing condensation, and, by this means, the down stroke would be produced by atmospheric pressure. This plan involved two important suggestions:-1st. The application of a piston working in a cylinder; and 2nd. The production of a vacuum by the condensation of steam. Papin prepared himself for the practice of medicine, and took his degree at Paris. He was a Protestant, and, in consequence of the Edict of Nantes, he was obliged to fly from his native country, and take refuge in England, where he became acquainted with that noble Christian man, Robert Boyle, and assisted him in several of his experimental researches. In 1681, he was elected a Fellow of the Royal Society. Some time after, he received the appointment of Professor of Mathematics at the University of Marburgh, and in that city he died, France, by thus persecuting for religious opinions, lost the honour of Papin's inventions and genius. Papin tried various plans for producing a vacuum under the piston 1. Gunpowder. 2. Water. 3. Some think he had an idea of the pump.

CAPTAIN THOMAS SAVERY (A.D. 1698).

Captain Savery was the first to take out a patent for a Steam Engine, and this forms the next important link in the chain of the progressive development of the Steam Engine. The object of Savery was to apply his machine to the raising of water from mines. The principle of the invention may be thus described :—

Two boilers were employed, the one for generating steam, and the other, which was much smaller, for feeding the large boiler with hot water. This was done by means of a connecting pipe, through which the fed water was forced by an excess of pressure in the small boiler. In starting the engine, the steam was allowed to enter a spherical copper vessel, or receiver, until it had driven out all the air, and ceased to be condensed against the cold sides, technically called "blowing through." The communication with the boiler was then closed, and a jet of cold water thrown upon the outside of the receiver, the contained

steam being thus partially condensed, and a vacuum formed, the water, meanwhile, rising into the receiver by the external pressure of the atmosphere. A communication was again opened with the boiler, and the steam pressing on the surface of the water in the receiver, forced it up a main pipe to a height proportional to its elasticity, its return inte the pipe being prevented by a valve opening upwards. By employing a double set of receivers to draw and force the water alternately, a constant ascending stream may thas be maintained. The boilers were fitted with watergauge cocks, for ascertaining the level of the water, and with the steel guard safety-valve, which had been previously invented by Dr. Papin for his digester. Savery's invention was due to an accident. He was one day in a tavern, and, having ordered a flask of Florence wine, he drank the wine and threw the bottle into the fire. A little wine was left in the flask, and presently Savery noticed steam issuing from its mouth. He put on a thick glove, took the bottle from the fire, and putting the neck in a basin of cold water, was surprised to find the bottle fill with water, the result of the steam condensing, and thus forming a vacuum, and the atmospheric pressure forcing the water up to fill the vacuum. Two objects were attempted by Savery-1st, raising water by atmospheric pressure, after producing a vacuum, to a height of about 24 feet; 2nd, lifting it still higher by the expansive power of steam. This engine, though displaying considerable ingenuity, was most defective in two points--1st, the great waste of steam (or fuel) caused by the condensation of the steam in a cold receiver, and its contact with the surface of the cold water: 2nd, the limited height to which a column of water could be raised, in consequence of the pressure of the steam being partly counteracted by the pressure of the atmosphere, to the extent of 15 lb. to an inch. Saverey's Engine, notwithstanding these defects, came into very general use; and there is no doubt it was vastly superior to anything of the kind previously invented. The term "horse-power" was first given by Savery, on account of the engine being designed to supersede horse labour, and was understood to mean a power equal to raising 23,000 lbs. of one foot high per minute. Boulton and Watt afterward fixed this at 33,000 lbs. raised one foot high per minute, and that is the standard of a horse-power now.

NEWCOMEN (A.D. 1705).

Thomas Newcomen and John Crawley, mechanics, of Dartmouth, in 1705 patented an engine that combined Papin's idea of the cylinder and piston, and Savery's method of producing a vacuum by condensation. Two great improvements were now accomplished by this. 1st. The steam was not condensed by contact with cold water; and, 2nd. The height of the column of water became independent of the pressure of the steam in the boiler. (That is, of course, presuming the size of the cylinder was increased in proportion to the load.) The cylinder was open at the top, and was supplied with steam at a low pressure by means of a pipe from the boiler to the bottom of the cylinder, the valve being worked by hand. When the engine was started, the steam was admitted into the cylinder, and the cylinder thus heated. The air was then expelled through the "blow-cock" valve in the cylinder bottom. Suppose the piston then lifted to the top of the cylinder, by means of the pressure of steam, it (the cylinder) is, of course, then full of steam. The communication with the boiler was then closed, and a supply of cold water was admitted into an outside casing round the cylinder, and, the steam being thus condensed, the down stroke was effected by atmospheric pressure. This engine was supplied with a beam and pumps, and was thus a great improvement upon Savery's plan. The weight of the pumps, of course, assisted in the down stroke. A small quantity of water was kept over the piston, to keep it air-tight, and a small cock and pipe at the bottom of the cylinder to draw off the water formed by the condensed steam. This was afterwards improved by injecting cold water into the cylinder.

Newcomen encountered great difficulties. His first attempt was to drain a mine at Griff, in Warwickshire, where 500 horses were employed for that purpose. Here he was unsuccessful, chiefly from defects in his pumps. In 1712, he was assisted by Mr. Potter, of Bromsgrove, and they were then successful in draining a mine near Wolverhampton. By an accident, they found out that they could make the engine work faster by applying the cold water inside the cylinder. While their engine was working, they found it all at once go much faster, and, upon searching for the cause, found a hole in the cylinder, which admitted the

cold water from the outside casing, and this, producing a quicker vacuum, caused more strokes per minute. They also found out, by accident, the plan of making the engine self-acting, by having a rod connected with the beam, to open and shut the valves. Up to this time, boys were employed to open and shut the "cocks," to make the engine work. One of these lads thus employed was a boy named Humphrey Potter, who, being more fond of play than work, contrived, by means of a string, to fasten the valve he had to attend to the beam, and thus to make the beam do his work. This apparatus was called a 66 Scoggan," and led to the introduction of the upright rod working the valves by means "toppets."

In 1718, Mr. Henry Brighton, of Newcastle, made great improvements in this part of the engine, and also added a pump, worked by the beam, to lift the water above the cylinder to be used for injection.

Brindley, also, about this time, added an improvement in the "water feed" for the boiler, which he made selfacting by means of a float in the boiler communicating with a valve in the feed pipe, and thus regulating the supply of water. After this, there were few improvements for the next fifty years; but during this interim, however, great improvements were made in the details of the steam engine, and attention was frequently called to the subject, arising from the constant difficulties that were experienced in the draining of our mines; and the period was fast approaching when Providence saw fit to raise up a man whose improvements in the steam engine were to immortalise his name, and greatly advance the interests and prosperity of his country-I refer, of course, to James Watt; but as his life and labours are quite deserving of a separate lecture, I must defer a description of his improvements in the steam engine to a future lecture, and close for the present by referring to

SMEATON (WHO WAS BORN A.D. 1767).

Smeaton, who, while employed by the New River Company to erect an atmospheric engine, brgan to direct his attention to the subject of the steam engine, and succeeded in making several improvements, the chief of which were -1st. The "Cataract," the parent of that part of the engine still bearing the name, and which regulates the strokes