In the year 1756 a patent was taken out by Mr. Blakey, for a contrivance which prevented the steam from coming in contact with the water, as in Savery's engine. One of his contrivances consisted in inter posing a quantity or oil between the steam and the wa ter. Ile employed also two receivers or cylinders, the one placed above the other, so that the water beneath the oil might not be changed at each injection. Ano ther contrivance was to interpose air in place of oil ; but none of these were found to answer in practice, and Blakey's engine never attained any celebrity. In principle, indeed, it was the same as Savery's. At a much later period, viz. in 1775, Mr. Blakey made an important improvement in the boiler, whereby much fuel is saved. Three cylindrical vessels were placed, the one above the other, as shown in Fig. 2. Plate DVI, and connected so as to constitute a boiler. It is then surrounded with the fire, and the steam let off by the cocks shown in the figure.
In the year 1757 Mr. Keane Fitzgerald communi cated to the Royal Society of London, a paper entitled .qn attempt to improve the manner of working the ven tilator by the help of the Fire Engine.* " As the lever of the fire engine works up and down alternately, and performs at a common medium about a dozen strokes in a minute, it was necessary to contrive some way to make the beam, though moving alternately, to turn a wheel constantly round one way, and also to increase the number of strokes to 50 or 60 in a minute. The model of a machine for this purpose, is composed of four wheels of different sizes, two clicks, three pinions and a fly, which is put into motion by the part of a wheel fixed to the arch of a lever of the fire engine. The wheel which is turned by the lever, or rather moved up and clown by it, is loose on its arbor, and likewise one of the ratchets, and the wheel next to it. The outside ratchets and outside wheel are fixed on the arbor. There are two pinion wheels fixed on the ar bor, one on each side near the edge of the wheel moved by the lever which turns them. There are also two clicks, one fixed to the great wheel, the other to the frame. These are exclusive of the wheel that moves the fly.
The effect is, when the lever moves the wheel downwards, its click forces the .ratchet fixed on the arbor to more along with it, and the other wheels the same way. When it moves upwards, the click fixed on the frame stops the larger ratchet, and the wheel next to it, which are pinned together. This wheel being stopped, and the great wheel carried upwards by the lever, the pinion towards the edge of the great wheel is forced round it, and moves the pinion on the other side of the great wheel, which pinion moves the wheel fixed on the arbor the contrary way to the great wheel, which is carried upwards by the lever. By which means the arbor is constantly turned the stifle way, when the lever of the fire engine is moved either upwards or downwards.
Upon the arbor, there is also another great wheel fixed, which turns a pinion, on the arbor of which pinion is a crank to move the ventilator, and also a fly fixed to the end, to help the motion of the crank, which, in the model, is turned three times for each stroke of the lever, and may be increased or diminish ed according to the number of teeth in the pinion. The number of teeth in the great wheel moved by the lever is 66, but need not have teeth above half way round. The wheel fixed to the ratchet has 33 teeth, and its pinion 11. The wheel fixed on the arbor on the outside has 24 teeth, and its pinion 16. The wheel
which turns the fly has 90 teeth, and the pinion turned by this wheel to. 'I'he greater the number of teeth in the ratchets the better. This machine may also be applied to other useful purposes at mines, and may easily be made to turn a mill, to grind corn, or to turn a wheel to raise coals, or whatever else is wanted to be raised from the mines." Dr. Robison had, without due consideration, re garded this contrivance of Mr. Fitzgerald as involving the invention of the crank, with which Mr. Watt had afterwards converted the vertical motion of' the piston into a rotatory motion, and had therefore deprived Mr. Watt of that honour. Mr. Watt, who, as it will afterwards be seen, had been particularly harassed re garding the subject of the crank, corrected to a cer tain degree this error in his annotations on Dr. Robi son's paper; but in a letter which he wrote to Dr. Brewster, dated February 23, 1814, he speaks still more decidedly:" Dr. Robison," says he," mentions, that Mr. Keane Fitzgerald published in the Transac tions, ' a method of converting the reciprocating mo• tion of the steam engine into a continued rotatory motion, by means of a crank, or a train of wheel work,' and adds, in sec. 52, by this contrivance he hoped to render it of most extensive use, and that he, and others associated with him, obtained a patent for it. They also published proposals for erecting mills of all kinds driven by steam engines, and stated fairly their powers and their advantages.' " Now, I find, (continues Mr. Watt,) in the Philo sophical Transactions, vol. 50, part ii, an invention by Mr. Fitzgerald for working ventilators by means a steam engine, in which the rotative motion is pro duced by a train of wheel work, which ultimately turns a crank, which works the ventilators, a very different thing from a rotatory motion produced by the inter vention of a crank! As to the mill scheme, we can find no trace of it, nor of the patent; and being a matter of some consequence to clear up, I have written to some friends in London about it, but have yet received no answer. I shall thank you, if you cannot otherwise find out the matter of fact, to get a search made among Dr. Robison's memoranda, to learn upon what au thority he made the assertion. If nothing more is learned about it, I must conclude the note to be a mis take, and comment upon it accordingly." No record of a patent was found at the public offices, and Mr. Watt accordingly made those alterations, &c. on Dr. Robison's paper, which are already before the public." It is impossible to pass over this statement respect ing the crank, without calling the attention of the reader to the annoyances to which an inventor is ex posed by the rash decisions and criticisms of his friends. If Dr. Robison and Mr. Stuart, men of talents and character, and great admirers of Mr. Watt, have, under a sense of justice, attributed one of his finest inventions, the one to Mr. Fitzgerald, and the other to Jonathan Hulls, without any other foundation than the recommendation of a crank, as part of the machinery, it is not to be wondered at that writers of inferior judgment and integrity should so often com mit the same mistake. To this species of persecu tion, Mr. Watt has been particularly exposed, and yet the whole history of science does not present to us an individual whose inventions were more original, and to which less approach had been made by the inge nuity of his predecessors.