2

In the well known Pendulum Governor of Watt, the centrifugal force operates to counteract an increased speed of the machinery with which it is connected, by overcoming the force of gravity.

Ingenious as this contrivance undoubtedly was, and to a certain extent efficacious, yet it had not been employed long before it was found to possess inherent defects, and that its action produced a constantly varying, rather than a regular motion. The cause of this is mainly attributable to its extreme sensibility and delicacy of action, by which an excess of motion in either direction continually occurs, producing a series of variations in the speed of the engine, which scarcely ever settles down to a regular rate of motion, unless the production of steam and the work performed, are of themselves constantly uniform.

In consequence of these defects, numerous attempts have been made to improve the governor; two recent patents for this object were duly noticed in our pages, and we gave at considerable length in our last volume (p. 370) the ingenious contrivance of Mr. Hick, in which the atmospheric resistance to rapid motion, is employed instead of the centrifugal force, to overcome the force of gravity.

By the arrangements which Mr. Hick has adopted, gravity, although still a constant force, was capable of being controlled by the quantity of opposing surface brought into action, so that by varying the angle of the fans or vanes, a capability of adjustment was afforded, not readily attainable in the original form of apparatus.

In the governor which we have this week the pleasure of laying before our readers, this capability of adjustment is still further increased, as the resistance to centrifugal energy (which is in this case a spring) can be increased or diminished to any required extent.

This simple and ingenious piece of apparatus is the invention of Mr. Henry Davies, the inventor and patentee of the Disc steam-engine, now attaining considerable celebrity, and to which we shall probably hereafter have occasion to call the attention of our readers.

By reference to the engraving on our front page the construction and operation of this governor will be easily unders'ood. It consists of an upright spindle AA, near the top of which are two equal horizontal arms, BB, furnished with stops at their extremities. Two weights CC run freely to and fro upon these arms by means of internal anti-friction wheels. D is a collar sliding upon the spindle suspended by two cords on chains, ff, which pass over two pullies (one seen at g) and are attached to the weights CC. A spiral spring, e, rests at bottom upon the collar D, and abuts at top against a sliding stop, L, which can be fixed at any required elevation upon the spindle by a set screw. H is the throttle valve lever with its forked end embracing the groove in the collar, D. I is a supporting arm, and K a pulley for receiving motion from the crank shaft of the engine.

The stop L having been set so as to cause the spring to press down the collar D, with any approved force, and the throttle valve opened to the required extent, the engine may be started. Should its speed exceed the stipulated rate, the increased centrifugal force will cause the two weights to recede from the spindle, which raising the collar D, will partially close the throttle-valve and diminish the supply of steam, when, the motion being checked, the spring will press down the collar and withdraw the weights until the desired rate of motion is obtained.

The degree of force exerted by the spring will of course always require to be adjusted to suit the nature of the work thrown upon the engine, because a small quantity of steam will be required when the work is light, and a larger quantity when it is heavy, while the speed should in each case be the same, a position which this kind of governor can be made to realise with great facility and remarkable precision.

In point of simplicity of construction and cheapness, as well as in the perfection of its action, this governor seems to have a decided advantage over all former contrivances for the same purpose, and we have no doubt will soon come into very extensive use.

3

Sir, The phenomenon of what is called "dry rot" in timbers has been often lamented, but almost invariably misunderstood. Certain harmless plants, such as the merulius destructor, and merulius lacrymans, (so called from the quantity of liquid which replenishes the hymenium,) the latter a misnomer when connected with the dry rot. These plants are held up to public execration as the delinquents, and as chargeable with the work of destruction. They stand, however, fully acquitted in the eye of science, as the deed is already done before they make their appearance, even in embryo, though their rudiments, in seeds, are already there. Like "the worm of corruption," they riot on decay,-it is the matrix wherein they germinate; but the disintegration of the organized structure has been already consummated.

It is assumed by Mr. Kyan that the cause of dry rot is to be sought for in the decomposition of the albumen of the sap; and the chloride of mercury, by combining with this albumen, and thus forming a substance undecomposable by the usual agencies of decay, constitutes the principle of his patent. Doubtless albumen may be arrested in its tendency to decay by chloride of mercury, or corrosive sublimate.

It is,

however, sheer assumption to say that dry rot has to do with the albumen of the sap. Sir W. Burnet, in his counter patent, I believe employs a salt of zinc.

The great expense of mercury, the price of which is considerably enhanced by the monopoly of Rothschild, forms a serious obstacle to Kyan's plan, and the price of the shares of the Patent Anti Dry Rot Company shows that great success does not follow their enterprise. Knowing that Sir H. Davy had selected chloride of mercury for a similar purpose, but very properly abandoned it from a conviction that it would form a deleterious and destructive atmosphere of mercurial vapour, I ventured to oppose it on the same grounds, contending, that in tropical climes, it would be as poisonous as the quicksilver mines of Idria, in Illyria, independent of its ready decomposition by the contact of iron and alkalis. As a matter of course, Mr. Kyan was quite furious, and summoned to his aid Dr. Birkbeck,

who attacked my position through the medium of the Morning Post. It turns out, however, that I was correct. There is, unhappily for the cause of truth, and advance of genuine knowledge, much favouritism in relation to the authority of a name, and party spirit runs as high in the coteries of science, as in the region of politics. Sir John Barrow, in his life of Lord Anson, has entirely impugned the efficacy of Kyan's process. The Duke of Portland had done the same thing in 1838, and to the same effect are the conclusions of Earl Manvers. Dr. Moore, in like manner, in his experiments at Plymouth, had shown that "Kyanised wood," as it has been called, is no proof against the ravages of the teredo navalis or shipworm, which was honey-combed like

the rest.

The experiments made at Welbeck in the mushroom house are very instructive and important, and appear to be entirely conclusive. Good Baltic timber in these trials, lasted longer than the best "Kyanised" oak. "Kyanised" and unkyanised oak decayed equally fast. It appears, too, that wood impregnated with Sir William Burnet's solution, and that which was not so treated, decayed alike. On the other hand it was proved that Scotch fir deals, and copperas, (i. e. sulphate of iron,) with lime water, resisted decay longer than any of them. It may be added that I had proved experimentally that sulphate of copper, also chloride of copper, would coagulate albumen, and therefore that this property did not exclusively pertain to corrosive sublimate, consequently that either of these might be substituted for it.

I may add, in this place, that Dr. Boucherie proposes to impregnate the tree, either by the root or by the bole, with a solution of impure pyrolignate of iron, prior to its being cut down. These two salts of iron are identical in their operation on the sap of the tree, and mutually illustrate the action of each other.

Fifteen years have elapsed since I communicated to the Admiralty, through Sir John Barrow the secretary, as a prophylactic, or preventive of "dry rot," the very agent, namely sulphate of iron, &c., which has thus been proved

ADCOCK'S PATENT SPRAY PUMP.

The following extract from a communication by Mr. Adcock, which appeared in the last number of the Mining Journal, fully illustrates the construction and action of his patent Spray Pump, of which we inserted a descriptive notice in a recent number.

"This wood-cut is intended to represent and explain a plan put down by me at the 100-yard shaft, at Pemberton, to relieve the bend pipe and lower part of the apparatus from any water that might, from accidental or other cause, be there collected; and as it answers the intended purpose well, I have no doubt the wood-cut, and its descriptive account, will be gratifying to many of your readers.

"In the wood-cut a b c represents a part of the downcast pipe, or the pipe that conveys the air from the top of the pit, or the galleries and workings of the mine, through the bend pipe into the upcast; b to c the bend pipe, or that which unites at the bottom of the pit the downcast with the upcast; cde the upcast pipe, or pipe through which the air, and the water commingled with it, is carried to the surface or top of the pit, that the water may be there again collected in a solid body, and thence be allowed to flow freely away; 6 6 represent five slits, through which the water flows from the sump or well at the bottom of the pit into the upcast pipe, when the apparatus is in action, that it may, by the current of air, be dispersed into drops, like drops of rain, and conveyed to the top. The downcast pipe is 29 inches diameter-the upcast pipe 17 inches; and when not working, and from causes which it is not necessary to explain, water leaks from the sump into the apparatus, to a height equal to the head of the water there, which is about eight feet from the bottom of the bend, or 8 ft. 7 in. from the bottom of the pipe beneath the bend, consequently, the water rises to the same height in the pipe g g g g, which is four inches diameter; m m is a pipe, twenty feet long, that receives a supply of water from a water ring, placed so as to receive the water that oozes through and trickles down the sides of the pit. This pipe also is four inches diameter, but is unnecessarily large; it terminates in a compound cone, marked n, as shown in the figure. Of the smaller cone the dimensions may be thus stated:-Its greater diameter, th of an inch; its smaller diameter, th ditto; and its length ditto. Of the greater cone, the dimensions may be thus stated :—Its smaller diameter,th of an inch; its greater diameter, 1th ditto; and its length, 54th ditto. A pipe, th of an inch diameter, descends from the junction of the larger cone with the smaller into the four-inch pipe, gggg, as shown by the woodcut. This pipe is nine feet long.

"Having thus given the proportions, I have only to describe the rationale of the contrivance:-The water in the pipe, m m, is maintained by the water ring, or by the water that oozes through and trickles down the sides of the pit to