such a manner, that when the wheels D a, D, and D6 move backward or forward, they keep the fans IIIIII in a direct motion.

Fb is a rope going from H b to D b, that when the wheel Da, D, and D b move forward, moves the wheel H 6 forwards, which brings the fans forward with it.

Fa is a rope going from the wheel H a to the wheel Da, that when the wheels D a, D, and D b move forward, the wheel H a draws the rope F, and raises the weight G, at the same time as the wheel Hb brings the fans forward.

When the weight G is so raised, while the wheels Da, D, and D 6 are moving backward, the rope F a gives way, and the power of the weight G brings the wheel H a forward, and the fans with it, so that the fans always keep going forward, notwithstanding the wheels D a, D, and Db move backwards and forwards as the piston moves up and down the cylinder.

L L are teeth for a catch to drop in from the axis, and are so contrived that they catch in an alternate manner, to cause the fans to move always forward, for the wheel H a, by the power of the weight G, is performing his office, while the other wheel, Hb, goes back in order to fetch another stroke.

The weight G must contain but half the weight of the pillar of air pressing upon the piston, because the weight G is raised at the same time as the wheel

Hb performs its office, so that it is in effect two machines acting alternately by the weight of one pillar of air, of such a diameter as the diameter of the cylinder is.

If it should be said, that this is not a new invention, because I make use of the same power to drive my machine that others have made use of to drive theirs for other purposes, I answer, the application of this power is no more than the application of any common and known instrument used in mechanism for new-invented purposes.

Answers to some Queries that have been made concerning the Possibility and Usefulness of this Undertaking.

Query I.

Is it possible to fix instruments of sufficient strength to move so prodigious a weight as may be contained in a very large vesssel ?

Answer. All mechanics will allow it is possible to make a machine to move an immense weight, if there is force enough to drive the same; for every member must be made in a proportionable strength to the intended work, and properly braced with laces of iron, &c., so that no part can give way or break. If the braces, &c. necessary for this work had been put in the draught, it would have been so much crowded with lines, that the main instruments could not be so well perceived.

Query II.

Will not the force of the waves break any instrument to pieces that is placed to move in the water?

Answer.-First, It cannot be supposed that this machine will be used in a storm or tempest at sea, when the waves are very rough; for if a merchant lies in a harbour, &c. he would not choose to put out to sea in a storm, if it were possible to get out, but rather stay until it is abated.

Secondly, When the wind comes a-head of the tow-boat, the fans will be protected by it from the violence of the waves; and when the wind comes sideways, the waves will come edgeways of the fans, and therefore strike them with the less force.

Thirdly, There may be pieces of timber laid to swim on the surface of the water on each side of the fans, and so contrived as they shall not touch them, which will protect them from the force of the

waves.

Up in-land rivers, where the bottom can possibly be reached, the fans may be taken out, and cranks placed at the hindmost axis to strike a shaft to the bottom of the river, which will drive the vessel forward with the greater force.*

It is a very curious fact, that a patent has lately been obtained for this mode of impelling vessels; and a

I

Query III.

It being a continual expence to keep this machine at work, will the expense be answered ?

Answer. The work to be done by this machine will be upon particular occasions, when all other means yet found out are wholly insufficient. How often does a merchant wish that his ship were on the ocean, when, if he were there, the wind would serve tolerably well to carry him on his intended voyage, but does not serve at the same time to carry him out of the river, &c. he happens to be in, which a few hours' work of this machine would do. Besides, I know engines that are driven by the same power as this is, where materials for the purpose are dearer than in any navigable river in England; therefore experience demonstrates, that the expense will be but a trifle to the value of the work performed by those sort of machines, which any person that knows the nature of those things may easily calculate.

Thus I have endeavoured to give a clear and satisfactory account of my new-invented machine, for carrying vessels out of and into any port, harbour, or river, against wind and tide, or in a calm ; and I doubt not, but whoever shall give himself

nearly similar species of locomotion has formed the groundwork of another patent for engines on land.-Editor.

the trouble to peruse this Essay, will be so candid as to excuse or overlook any imperfections in the diction or manner of writing, considering the hand it comes from: if what I have imagined may only appear as plain to others as it has done to me, viz. that the scheme I now offer is practicable, and if encouraged will be useful.*

* The plain good sense evinced by the projector of steam navigation, and the very palpable truth conveyed in the last sentence of this admirable little Treatise, furnish the clearest evidence of the justice of our claim to the priority of invention, and awards to Great Britain a new link in the history of her naval triumphs.

In concluding this important subject, we must not, however, forget to notice the spirit of prophecy displayed by Dr. Darwin at a subsequent period. It occurs in the "Botanic Garden," and is to the following effect:

"Soon shall thy arm, únconquered Steam, afar!
Drag the slow barge, or drive the rapid car;
Or on wide waving wings expanded bear

The flying chariot through the fields of air."

The propulsion of boats by steam, like that of carriages, has long ceased to be problematic; and it is a curious fact, that Sir George Cayley, having entered into a mathematical investigation of the powers of steam machinery when compared with the muscular force of birds, has come to the conclusion, that such an attempt is not merely feasible, but might be undertaken with every possible chance of success.-Eliter.