care in the manufacture of the engine, simplicity of construction, together with great care in the arrangement of the pump-work, he attained the enormous duty of 87 millions-doing as much work with one ton of coal, in 1828, as was accomplished with four tons in 1815. No improvement of consequence in the Cornish single-power pumping-engine has taken place since that time. Some few engines have occasionally been reported highercaused by working with a higher degree of expansion, or by having superior fuel, and by having the proper maximum of work to do; but it may be fairly said, that Capt. Grose brought the Boulton and Watt single-power pumping-engine, as used in Cornwall, to a state of perfection, which has received no further improvement so far as regards duty-for the last twenty years. Although the duty of the single power pumping-engine was not got to so high a state of perfection, there was room left for a very important improvement in the stamping and winding enginesthe average duty of stamping-engines at that time being no more than about twenty millions; and that of the winding-engine much below. I therefore suggested the propriety of carrying out the same principle in those engines; and, in 1825, I erected a stamping-engine at the Charlestown Mines, near St. Austell, which answered my most sanguine expectations-having performed upwards of sixty millions.

Messrs. Hocking and Loam have carried out this principle in the winding-engine to a greater extent than any other party, and have realized a duty in just the same proportion. Having shown that there is a very great saving effected by the long-stroke expanding engines, I think it my duty to point out some of the inconveniences attached to this mode of using steam-power.1. As regards the pumping-engine, the strength of engine and pumpwork must be increased in proportion to the rate of expansion; this, together with the increased length of stroke, causes considerable extra expense.-2. As the load of the engine increases by the increased depth of the mine, the engine, with boiler and pump-work, become weaker by age and wear; hence, when economy is most required, it is least attainable: and this is frequently shown in our best engines by the duty.-3. The power of the engine is less in proportion to the rate of expansion, because it must be evident that, at whatever portion of the stroke the steam is cut off, the power of the engine must be lessened in proportion.-4. The violent concussion given to the material in the engine and pump-work at every stroke the engine makes, and which is in proportion to the rate of expansion, frequently deranges the machinery, thereby causing expensive accidents, and long and expensive hinderances to the mine. These facts induced me, some few years ago, to turn my attention to some mode of carrying out the expansion of steam to equally as great extent, without so much danger to the material; and this I have

done with my improved combined engine, where, for a given load, instead of the full force of the steam acting on the upper side of one piston only, it is in the combined engine for the same load divided-first acting on a small piston for the down stroke, and the same steam again acting on a large piston for the up strokeconsequently giving the steam equal, or, in some cases, greater expansion, without any danger to the material by concussion; and I would remark that the steam, having first expanded in the small cylinder, again expands throughout the whole stroke of the large cylinder-gives as much expansion in a 6-feet stroke as can be obtained by a 12-feet stroke in the single-acting engine. I believe the manner in which this engine is constructed is well known; it has, of course, two cylinders, one fixed on the top of the other—the bottom cylinder being about four times the area of the top cylinder. For all small engines, it is not necessary to make two cylinders, but cast it in one-the bottom part being about four times the contents of the top one. This engine will then differ from the single-power pumping-engine only by having the bottom part of the cylinder larger than the top, and two pistons instead of one; but with one piston-rod, and nearly all the other things, as the single-acting engine.

In pointing out the advantages of this engine, I do not claim a higher duty, by a given quantity of coal, than can be obtained by a very long stroke, and highly expansive Boulton and Watt engine; but I do claim a duty equally high, with a very much better application of the steam, as regards the general safety of the material, and also for increasing loads, as all mining engines are subject to; but, although I do not claim a higher duty with the combined engine, when compared with the long-stroke expanding engine, it is when put in competition with the doublepower Boulton and Watt rotatory engines, working in the ordinary way, as in general use in factories, flour-mills, &c., throughout the kingdom, varying in length of stroke from 3 ft. to 6 ft., and without the benefit of working expansively, and also with marine engines, where the stroke is necessarily short-consequently little benefit from expansion. The saving of fuel, when compared with these engines, is enormous, and which is shown in the following testimonial from Mr. Hawksley, an engineer of considerable eminence :

"Nottingham, March, 6th, 1848.-I have much satisfaction in reporting to you the excellent duty performed by the combined cylinder engine, manu. factured by the Messrs. Harvey and Co., under your patent, and erected by me at the Coventry Water-Works. On a recent occasion, 1 ton of coal, weighed into the boiler-house, maintained the engine in action for 15 hours, while making 12 strokes per minute, in a double-acting pump, of 16 in. diameter, working under the pressure of a column 150 ft. high. This is equal to only 4 lbs. per horse-power per hour, instead of 10 or 12 lbs. per horse-power per hour, usually consumed by good engines of the ordinary kind. The coal used was very inferior to the Welsh, the Newcastle, or the

best Lancashire. Had we employed fuel of a superior description, the con-
sumption would certainly not have exceeded 3 lbs. per horse-power per hour.
The engine, when up to her speed, drives the fly-wheel with perfect regularity.
I have, therefore, no doubt of the applicability of your invention to manu-
facturing purposes. The results would be most valuable, both in regard to
economy of fuel, and the consequent diminution of the nuisance of smoke;
for, with the consumption of less than half the coals, there must, of course,
be less than half the smoke evolved.
"T. HAWKSLEY."

I have also a testimonial from Messrs. Mason, of Sudbury, in
Suffolk, equally satisfactory :-

"Sudbury Mills, Suffolk, November 4, 1847.-We have much pleasure in informing you that our combined cylinder engine, on your patent principle, is giving great satisfaction. It is now working four pair of stones, and the consumption of coal per hour is under 70 lbs., of the middling quality. We are quite satisfied it is the best sort of engine in use at the present time. "F. & P. MASON."

I would now beg to say that, whether the saving named by Mr. Hawksley can be effected by the combined engine, the longstroke expansive engine, or any other kind of engine, it is a matter of considerable importance to this great commercial country, where steam is so very extensively in use, that the matter should be investigated, and, if found correct, to be generally adopted. I have been informed that, in Manchester, and including a radius of 30 miles around that place, there are 4,000 steam-engines at work; and I believe I am quite safe in saying, that the average consumption of coal is full 12 lbs. per horsepower per hour. I will suppose them to average 20-horse power each, and that they are consuming 8 lbs. per horse-power per hour above the engines referred to in the testimonials, and that the average time of working is 12 hours a day, and six days a week, it will then be found that it will amount to the astonishing quantity of 1,069,714 tons per year, which at 5s. per ton is £267,428. I say again, that, whether it is a combined engine, or any other kind of engine, that will effect such an immense saving, the system, fully carried out, would, in a commercial view of the matter, be of vast importance to this country.

In the marine engines, as now constructed, the expansion principle cannot be made available to any great extent, in consequence of the shortness of the stroke; the consumption of fuel, therefore, is very great. The combined engine, working wholly expansively in the large cylinder, I find the economy of fuel just the same in short-stroke as in long-stroke engines-as a proof of which I have a letter from Ipswich, informing me that the two combined engines, lately erected on the town mills in that place, are not consuming so much as 34 lbs. per horse-power per hour; the stroke of these engines is only 3 ft. 6 in. Combined engines would save 40 per cent. over the present marine engines, and might be employed with horizontal cylinders, or in any other position, which might be found most convenient.

In the present state of Cornish mines-I refer to their great depth, and the very low price of their produce-I think it the duty of every engineer employed in these mines to pay every attention to economy in the construction of the steam-enginefor, however simply they may be constructed, they are still very expensive articles. There have been lately some few engines erected, which show there is a nearer approach to economy than heretofore; I refer to the inverted and direct-acting engines, which are far better, in point of economy and safety, for mining purposes, than the present lofty engines with their castles of houses some engines having a main beam, or bob, of twenty-five tons, shaking the whole building at every stroke it makes; but there is still a more economical engine for mining and other purposes, than the inverted engine-viz. the horizontal engine. The economy of such engines must be very evident-not only in the first cost of engine and house, but also in the economy of material and fuel; and I am happy to find, that I am not the only one that has begun to adopt this plan, as I find from Mr. Wm. West, that he has three combined engines of my patent now making, each of them to be laid down horizontally. The objection to horizontal engines has been the supposed wear of the cylinder and piston by means of the weight of the piston constantly bearing on the bottom side of the cylinder; but I find that practice proves it otherwise, and that the cylinder wears just as well as if vertical. This fact is accounted for as followsviz., the grease, or oil, with which it is lubricated invariably settles at the bottom, thereby causing the piston to be constantly moving in grease, or oil, and preventing any perceptible wear for many years. There may probably be a little more friction than in a vertical cylinder of the same size; but this is fully compensated, in the absence of a considerable amount of friction which necessarily exists in the vertical engine more than in this. I would beg to remark, that whether the engine is a single cylinder, or my combined cylinder engine, I would, for all mining purposes, fix them horizontally. These combined engines are in use for the following purposes :-For pumping, stamping, winding, grinding copper ore, weaving cloth and silk, driving machinery, and for agricultural work. The number erected is fifty-five, and there are several new ones now making.

ON THF STRUCTURE OF THE CRYSTALLINE ROCKS,

POLARITY OF CLEAVAGE AND PORES, AND THEIR INFLUENCE
ON THE FORMATION OF MINERAL VEINS.

BY E. HOPKINS, C.E., F.G.S.

THERE are three distinct planes of crystallization in the compound granitic base with reference to the globe, causing the mineral mass to form a geometrical structure, viz., the polar, the radial, and the concentric. The first are in lines more or less corresponding to the meridian; the second, in connection with the first, form the cleavage planes, the medullary rays, as it were, of the sphere; and the third, the concentric exfolia, similar to the position of sedimentary beds, fluids, &c. The efflorescence of certain minerals, metals, &c., from the surface, is, like vegetation, classed with those elements which during chemical activity produce the radial structure, as shown in the following diagrams.

N

S

A minute and careful examination of the crystalline film of the earth shows very clearly this phenomenon of order, and distinctly shows the influence of the great polar force in the molecular arrangement of the semi-fluid substances which constitute the surface of the sphere.

The cleavage planes in all parts of the world are more or less vertical, as shown in the middle figure (the equatorial section), and but slightly deviating in their direction from the meridian, as marked on the first figure. In the primary rocks from the Straits of Magellan to the Caribbean coast, the cleavage planes preserve a geometrical parallelism through all the series of rocks they intersect. Again, in the Isthmus of Panama, Mexico, and North America, whatever be the contortions of the chains or the configuration of the lands, the planes of cleavage pass on without much deviation, running in parallel lines in a direction a few degrees east of magnetic north, and in planes more or less vertical. The same phenomenon has been observed in Australia, in Asia, and throughout all Europe, where the granites and primary