petition, necessarily insure inspection, inasmuch as the number of explosions being one in 2000 boilers per annum, it follows that the net cost of insurance is only one shilling for every £100, which must evidently be inadequate for any description of inspection by way of prevention. Insurance, therefore, as previously pointed out, is cheap, while adequate inspection is costly; so that inspection is opposed to dividend, for which joint-stock companies are clearly established. Some corrective, therefore, is plainly necessary, and this it is thought would in some measure be found by the establishment of a fixed substantial penalty in the event of every explosion, irrespective of the amount of damage done. Also the imposition of a penalty on every inspection-association or insurance company failing to prevent the explosion of a boiler under their care, might have a most wholesome tendency, this penalty being equal and in addition to the one imposed on the owner, and, in like manner, devoted to the support of the compensation fund *.

In conclusion, although entire assent cannot be accorded to the Parliamentary Report, yet it is most cordially wished that every success may attend the adoption of the measures recommended therein, and that they may result in preventing many explosions, and in diminishing the lamentable loss of life at present resulting from the constant recurrence of these catastrophes.

On Designing Pointed Roofs. By THOMAS GILLOTT.

Description of a Salmon-ladder meant to suit the varying levels of a Lake or Reservoir. By JAMES LESLIE, M.I.C.E. (Communicated by ALEX. LESLIE.) So long as the reservoir or lake is full and overflowing the fish may ascend the waste weir if not too steep, and if otherwise properly constructed and furnished, where necessary, with a salmon-ladder; but whenever the water ceases to overflow the waste weir, the means for the ascent of the fish are generally cut off.

The sluices at the outlet of a lake used as a reservoir are in general (though there may be exceptions to the rule) placed at or near the lowest level of the outlet, and the velocity of the current through them is consequently, in most cases, so great that no fish can swim against it until the surface of the water be run down so low as to be near the level of the outlet, and the velocity be thereby reduced; and in that latter case the power to ascend into the lake is of no great value, as the salmon have little or no disposition to run during droughts.

This design consists of a series of sluices placed side by side at different levels, each sluice opening by being lowered instead of by being raised, as is the general mode, and each commencing with the salmon-ladder, which passes along in front of the sluices, and is composed of alternate pools and falls. In this design it is contemplated that on all occasions the whole outflow required to run down the stream should be through only one sluice at a time, and over the top of that sluice, which would open by lowering, and shut by being raised, except in extreme floods, when, for the sake of keeping down the level of the lake, so as to avoid flooding the adjoining lands, or for any other similar reason, it may be necessary to provide a lower outlet, or the means for a more rapid discharge for the water.

Assuming an instance of a lake with a rise and fall on the surface of 12 feet, and that it is full, or just up to the level of the waste weir, the uppermost sluice of the series is opened so that the water may flow over it to the depth of, say, 9 or 12 inches, which depth we may assume to be necessary to give the statutory compensation. The water will then run down the ladder, which is composed of a series of pools formed by stops reaching quite across from wall to wall, the fall from surface to surface of those steps being 18 inches, and the depth of the pools not less than 3 feet. A fish may then easily leap over the successive falls from the lowest to the highest, after which they must take the last leap over the outlet sluice into the lake, that last leap being at first like all the others, 18 inches, but

The exemption described above in favour of steam-users should also apply under similar circumstances to Inspection Associations or Insurance Companies.

diminishing in height as the level of the lake is lowered, till at last it is nothing, when the level of the lake comes to the same as that of the highest pool. After that, when the surface of the lake gets too low to give the statutory or requisite supply of water over the uppermost stop, the uppermost sluice is shut, and the one next in order of descent is opened, when the fish would have one leap fewer than before, entering the lake by leaping over the second sluice, and then in succession as the level of the lake falls over each of the other sluices, having a leap less at every change, till at last, when the lake comes to be lowered to nearly the level of its lowest outlet, there would be only one leap to take.

On a new System of Warming and Ventilation. By J. D. MORRISON. The author called attention to his paper which was read at the Exeter Meeting, and stated that he introduced improvements which had been approved of by the Highland and Agricultural Society of Scotland. He had also built an experimental room, where his system of ventilation might be tested practically.

Chain-Cable Testing, and proposed New Testing-Link.
By R. A. PEACOCK, C.E., F.G.S.

It is proposed to provide "testing"-links for each new cable, one link to be connected with the cable at each of its ends, and another link to form part of the cable at every 15 fathoms. Each new link will be a flat oval piece of wrought iron, whose thickness will be equal to the diameter of the metal of each ordinary link. The new links will be cut out of a plate of iron, by means of a steam-punch, and will be left by it of the oval form and having three circular holes through, one in the centre and another halfway to each end. The use of the centre hole, which will be 14-inch diameter for a 1-inch cable, is this:-a piece of cylindrical bar iron, about 6 inches long and a shade less than 11-inch diameter, is to be inserted into this hole, and by means of this bar one of the 15-fathom lengths can be connected with a hydrostatic press, the other end of the "length" being fastened at the opposite end of the platform by means of another 6-inch bar, and then the testingstrain may be applied. The two other holes are to connect the testing links with the adjoining parts of the cable.

A cylindrical bar of South-Wales iron was tested by the late Mr. Telford, and its increase of length was found to be 11.68 per cent. After the test, and its diameter was reduced from 13 inch to 11, it was torn asunder by 43 tons 11 cwt. Therefore if the "length" of 15 fathoms is increased by testing to an amount exceeding (say) 8 per cent. of its original length, its diameter, and consequently its strength, will have been too much reduced, and it ought to be condemned. When the stretching is confined within moderate limits so as to justify the tester in stamping and passing it, the actual length may be stamped on the testing-link; and then, when the cable has been exposed to severe strains on service, it may be laid straight along the pier, and each length be remeasured to ascertain if the strain has been too great, and if any part ought to be condemned.

Links have been found to be cracked after having apparently withstood the test: therefore each length, after being tested (before being stamped), should be lifted upon a well-lighted bench of the height of a table, and then every link should be examined carefully all over with a magnifying-glass. If any link is found to be cracked, or otherwise defective, the "length" of course ought to be rejected.

On the Carbon Closet System. By E. C. C. STANFORD, F.C.S.

On the Steam Blast. By C. WILLIAM SIEMENS, F.R.S., D.C.L., M. Inst. C. E. After describing what had previously been done by others, including the researches of Professors Zeuner and Rankine, the author explained an improved steamblast apparatus which he had invented. This apparatus consisted of three principal

parts, viz. :-(1) a steam-nozzle of annular cross section, discharging steam in the form of a hollow cylindrical body of a thickness of wall of not more than 02 (one fiftieth) of an inch; (2) a mixing-chamber, with contracted annular inlets for the air, equal in area to its least sectional area, and of a length equal to from five to six diameters; (3) a parabolic delivery-pipe of considerable length, in which the mixed current is gradually brought to the condition of comparative rest, and its momentum or living force is reconverted into potential force or pressure.

The result of a long series of experiments leads to the conclusions:-(1) That the quantitative effect of a steam-blower depends upon the amount of contact surface between the air and steam, irrespective of the steam pressure, up to a certain limit of compression, where the impelling action ceases; (2) that the maximum attainable differences of pressure increase, under otherwise similar circumstances, in direct proportion with the steam pressure employed; (3) that the quantitative effect produced is regulated (within the limits of efficient action of the instrument) by the weight of air impelled, and that therefore a better dynamical result is realized in exhausting than in compressing air; (4) that the limits of difference of pressure attainable are the same in exhausting and in compressing.

It was stated that with this apparatus a vacuum of 24 inches of mercury had been obtained, and that with two of these apparatus a working vacuum of 10 inches of mercury had been maintained at one end of a pneumatic despatch-tube 3 inches in diameter, through which carriers were propelled at the mean rate of about 1000 feet per minute.

Automatic Gauge for the Discharge of Water over Waste Weirs.
By THOMAS STEVENSON, F.R.S.E., M.I.C.E., C.E.

The author stated that, in order to ascertain the amount of available rainfall, which is so important in questions of water supply, it is necessary to gauge the quantity of water which escapes at the waste weirs of reservoirs. Observations made only once or twice a day cannot supply the information. It is proposed to place a tube perforated vertically with small holes, the lowest of which is on a level with the top of the waste weir, so that, whenever water passes over the weir, it also passes through the holes in the tube. The water is collected in a tank capable of holding the discharge for a certain number of hours; the quantity so collected is a known submultiple of what passes over the weir. The discharge through the holes is ascertained by experiment. This self-acting apparatus will render the continuous observations of floods unnecessary.

Thermometer of Translation for recording the Daily Changes of Temperature. By THOMAS STEVENSON, F.R.S.E., M.I.C.E., C.E.

The author described what he termed a thermometer of translation, which consisted of an expansible body with a needle-point at its upper end, and which, when expanded by the sun, is fixed at its upper end by a needle-point catching into fine teeth cut in a sheet of glass or other material of small expansibility placed below. When the sun is obscured, the upper end being fixed, the contraction raises the centre of gravity of the bar. In this way the daily march or creep of the bar chronicles the change or changes of temperature. Mr. Stevenson also described two different methods, suggested by his friends Professors Tait and Swan, for increasing the amount of expansion of the material employed.

On improved Ships of War. By MICHAEL SCOTT.

On a Road Steamer. By W. THOMSON.

The great feature in the construction of this machine is the use of a very thick. india-rubber tire, to the outer circumference of which is attached a chain of flat plates of iron. These india-rubber tires not only completely prevented hard shocks 1871.

16

to the machinery, but saved the road from the grinding-action of the iron wheels which was so injurious to bye-ways. There had been serious objections made to the use of these engines with rigid tires; but the author ventured to assert that the india-rubber tires not only did not injure, but actually improved the roads. The only ground upon which india-rubber tires did not work well was where the soil was extremely wet, or of a very soft and sloppy nature. For farm work, the wheels of the engine required a much thicker coat of india-rubber.

APPENDIX.

Notes on Dredging at Madeira.

By the Rev. ROBERT BOOG WATSON, B.A., F.R.S.E., F.G.S.

The difficulties of shell-gathering at Madeira are very many and very great. As the result of several years' work, the author has to record that six or seven species mentioned in MacAndrew's List have hitherto escaped him; that to the one hundred and twenty-seven species named by MacAndrew (besides these he gives twenty-nine unnamed = one hundred and fifty-six in all) the author has succeeded in adding something like two hundred and fifty more, or from three hundred and fifty to four hundred in all; and while these strongly confirm MacAndrew's generalization of the Mediterranean character of the Mollusca, yet a few of them present forms belonging some of them to the tropics, and others to very distant localities, as, for instance, Ranella rhodostoma and Triton chlorostoma, which Reeve, not perhaps very reliably, assigns, the first to the Islands of Capul and Masbate of the Philippines, and the second to the Island of Annaa in the Pacific. Further, among these two hundred or two hundred and fifty species, eighty or, perhaps, ninety may probably prove to be new species, and three or four new genera.

It is somewhat curious that only one of the author's new species has been recognized by Mr. Gwyn Jeffreys as obtained by him from the Porcupine' dredgings.

The publication of full details is contemplated by the author.

On the Ciliated Condition of the Inner Layer of the Blastoderm and of the Omphalo-mesenteric Vessels in the Egg of the Common Fowl. By B. T. LowNE. Mr. Lowne stated that the number of observations he had at present made were insufficient to substantiate his opinion beyond a doubt, but that he thought it extremely probable, from what he had seen, that, 1st, the inner layer of the blastoderm is ciliated, at least in tracts of its surface. He had several times observed the most marked currents, and he believed, but was not certain, that he had distinguished the cilia.

2ndly. From a single observation he thought that the interior of the omphalomesenteric vessels is ciliated. He saw in a portion of the blastoderm of a five-day chick the most marked circulation in the omphalo-mesenteric vessels. In one large vessel, especially where the two cut extremities were blocked with bloodcorpuscles, a rapid movement was taking place.

Mr. Lowne stated that he was still investigating the subject.

INDEX I.

REPORTS ON THE STATE OF SCIENCE.