Mr. Sturgeon has adopted very special cooling arrangements for his compressors. Firstly, the air used is all taken through the roof of the engine-house, and thus heating by contact with the boilers and engines below is avoided. It is filtered of deleterious dirt in entering through the roof. Secondly, the compressor cylinders are surrounded by ample water jackets, through which a continual fresh-water circulation is kept up. Thirdly, the delivery-valve-it is a single large disk of slightly greater diameter than the cylinder-is made hollow, and through it a cold-water circulation is kept up, the water being spread out in a thin radial stream across the valve face over which the air flows as it leaves the cylinder. This cooling-water is supplied to the hollow valve through a tube sliding in a stuffing-box in the cylinder cover. A further development of this system would be a supply of cooling water to the face of the piston after the manner

that the steam is supplied to the piston-jacket of the lowpressure engine cylinder; but this refinement has not been deemed necessary in the design as at present adopted.

The compressor piston-face travels a little beyond the position assumed by the flat face of this delivery-valve when the latter is closed. During the momentary pause at the end of the stroke, the valve therefore falls into actual contact with the piston-face, and the two descend together until the valve is landed on its seat. Thus the clearance space is reduced absolutely to zero.

The suction-valves are somewhat similarly arranged so as to reduce the clearance at the other end of the stroke to a very small amount. The cooling-water is circulated by gravity from a tank giving a head of 20 feet. The water is pumped into this tank from the canal, and the power spent in pumping this water is a partial set-off

against the economy resulting from the approximation to isothermal compression; but the power thus gained greatly outweighs the work spent in this pumping.

As at present designed, the air-pipes are of wroughtiron plate, riveted, but a new design for plate-steel tubes is being considered. The pipes are to be laid in concrete tunnels, which free them from all pressure of superincumbent soil or paving, and will always be very accessible for examination and repair. They are of 24 inches diameter near the central station, and diminish to 7 inches in the smallest branches. The joints are given a small degree of flexibility. In one design they are formed by two angleirons riveted to the outside ends of the two pipes, a hard rubber ring of circular section being placed between the flanges thus formed, and the flanges being drawn together by bolts. In another design a sort of double-socket coupling-piece covers the ends of both pipes for a few inches; the end of each pipe has formed on it two slightly

projecting rings, and between these is poured, in the molten state, through a hole in the socket-coupling, a soft metal that expands during solidification. We rather doubt whether this last design will give sufficient tensive strength to the joint. Tensive strength is required simply because there are necessarily bends in the pipe here and there.

The air is supplied to the consumer through a registering meter. This meter is similar in construction to Beale's gas exhauster. It consists of two cylinders, one inside the other. Both are 4 inches long; the outer one has a diameter of 14 and the inner a diameter of 9 inches. The outer one is fixed, and is furnished with an inlet and an outlet opening. The inner cylinder revolves freely on a fixed axis, distant (14-93)= 2 inches away from the centre of the outer case, so that the two cylinders always touch along a fixed line. Two sliding shutters project from a slot through the centre of the revolving

cylinder. By means of a pin and a pair of sliding blocks running in circular grooves cut on the inner surface of, and concentric with, the fixed cylinder, these shutters are drawn out and in from the revolving cylinder so as always to keep in contact with the fixed one. During one revolution these shutters sweep through the meter a volume of air about 17 cubic feet.

This rotation is reduced three times by worm-gearing in being transmitted to the counter-box, so that a single dial with two concentric circular scales, which are read by two fingers like the hour- and minute-hands of a common clock, is sufficient to register up to a million cubic feet. Fig. I shows this meter. It is driven by a small difference of air-pressure between the inlet and outlet.

The Company intend to charge at the rate of 5d. per 1000 cubic feet at standard pressure of 45 pounds per square inch. If the air were used in an engine without expansion, without clearance space, and without back pressure above the atmosphere, this would correspond to a cost per hour per indicated horse-power of

60 X 33000 × 5
= 1'53 pence.
144 X 45 X 1000

Under the conditions of actual practice the writer calculates that at the above rate of 5d. per 1000 cubic feet, assuming intelligent and economical management, each

pure rolling action at one or other side of its tread. The wearing might not be of much consequence in itself, except that it gradually vitiates the accuracy of the indication; and besides, the velocity ratio is uncertain because of the contact taking place over a perceptible range of radius. There ought to be an idle roller between the disks opposite the driving roller, and both disks ought to be pressed inwards by springs, instead of one only. But the chief defect is in the principle of the construction, which does not make the dial-indication proportional to PV as it ought to do. If Ro be the disk radius at which the roller would stand when zero pressure existed in the Bourdon tube, and if C be the inward movement per pound per square inch rise of pressure, and if be the radius of the roller, then at pressure P the contact radius on the disk will be Ro - CP, and the fractional revolution of the disk per revolution of the roller is This is not proR-CP portional to Pas it ought to be. Its differential coefficient with respect to P should be constant, whereas it is really The converse gearing ought to

Cr

r

(R-CP)2 be substituted; that is, the volume-meter should be geared positively with the disk, and the disk should drive

indicated horse-power will cost per hour from 2d. down to as low as Id., excluding cost of engine attendance and depreciation, and interest on first cost of engine.

The standard pressure at which the air is sold at the above price being 45 pounds per square inch, a reduction of price per cubic foot has to be made if the pressure of the sup supply be less than this pressure. This is effected by introducing a variable velocity-gear between the volumemeter and the dial-counter. This arrangement is shown in Fig. 2.

The rotation is transmitted to a small roller on a spindle capable of sliding in its bearings parallelly to its own axis. It drives a disk on the counter-arbour by rolling contact. The end of the roller-spindle is linked to the end of the tube of a Bourdon pressure-gauge. As the pressure rises, the roller is thus pushed nearer the centre of the disk, and gives this disk, therefore, an increasing fraction of a revolution per revolution of the roller. The roller really lies between two disks, but the one is "idle " and serves simply to support the roller in pressing against

the driven disk.

This integrator is wholly wrong in principle, and it is badly designed in detail. The roller has a rubber tyre round it, and therefore touches the disk at different radii, and thus must rapidly wear away, owing to the want of

FIG. 3.

the roller, the point of contact for zero pressure coinciding with the centre of the disk. It also seems a pity, when a Bourdon tube that measures the pressure exists in any case in the meter, that its measurement of the pressure should not be made visible by the simple addition of a pointer and graduated dial.

The registrations of all the meters in the whole district are telegraphed to the central station and added up on one large central counter, so that the engineers in charge may have means of continually comparing the actual consumption with the duty of the engines, known from ordinary engine continuous counters, and of detecting any serious leakage that might occur in consequence of breakage of a main or branch pipe. The telegraphing apparatus is shown in Fig. 3. The counting disk is divided into ten equal divisions, each representing 1000 cubic feet, by small metal projections. As these come successively underneath a contact-maker, they allow the passage of a current, which moves the finger of the central counter through a corresponding division. One main wire, with branches to the separate meters, is sufficient for the whole district, the earth return being used. As the counter-disk moves slowly, special means must be taken to break the

called "efficiencies" it is difficult to understand. The consumer is supposed to supply a large extra amount of power at his own cost by burning gas to heat the air, and it seems an extremely evident misuse of the word "efficiency " to apply it to the ratio of the diagram so got to the diagram of the central station engine. By a little more liberal burning of gas, the efficiency obtained by this method could quite easily be made higher than unity, On the same principle we might calculate the efficiency of a steam-engine by taking the ratio of the indicatorcard from the steam cylinder to that taken from the feedpump that supplies water to the boiler, and thus obtain an efficiency of, let us say, 50,000 per cent. This is a reductio ad absurdum of the method of calculation which is perfectly legitimate and logical. R. H. S.

THE CLASSIFICATION OF THE CÆCILIANS

IN a paper on the structure and affinities of the Amphiumidæ, published in the newly-issued part of the Proceedings of the American Philosophical Society (vol. xxiii. No. 123), Prof. Cope has put forward some views as to the position of the Cæcilians or Apodous Batrachians in the Systema Naturæ, which are worthy of careful consideration. The Cæcilians, Prof. Cope observes, are generally regarded as representing a distinct order of the Batrachian class, which bears the name "Apoda," or "Gymnophiona." The definition of this order given by Mr. Boulenger in his recently published Catalogue of the specimens of these animals in the British Museum is: "No limbs; tail rudimentary; males with an intromittent copulatory organ; adapted for burrowing." Of these definitions Prof. Cope maintains that not one is of ordinal value. "The tail in some Cæcilians is distinct. The intromittent copulatory organ in such species as Dermophis mexicanus, Gymnophis proximus, and Herpete ochrocephala is not a special organ, but merely the everted cloaca. The hard papillæ observed by Günther in Ichthyophis glutinosus are wanting in the above-mentioned species, and the protrusion of the cloaca is performed by two special muscles."

As regards the absence of limbs in the Cæcilians, Prof. Cope points out that the extremely rudimentary character of these organs in Amphiuma is well known, and that their non-existence has no greater claim to be considered as of ordinal value in the Batrachians than in the adjoining class of Reptiles, where it is in some cases not even a "family" character. Looking to these facts, Prof. Cope proposes to unite the Cæcilians with the Urodele Batrachians, and to class them only as a family, "Cæciliidæ," connected with the more typical forms of the group through the Amphiumidæ.

Messrs. Sarasin, who have recently published a most interesting account of their observations on the development of a species of Cæcilian in Ceylon, seem to have come to nearly the same conclusions as to the correct systematic position of this group of Batrachians.

NOTES

THE Prince of Wales has requested the President of the Royal Society to join the Committee appointed to advise on the organisation of the proposed Imperial Institute.

We have referred elsewhere to some of the possible results of the meetings held last week in favour of the Imperial Institute. Some very striking features which have been developed in connection with this movement during the last week are, first of all, the considerable desire which has been evinced to enrich various localities with some Jubilee memorial, and, again, the wisdom

"Ueber die Entwicklungsgeschichte von Epicrium glutinosum," Arb. Zool. Inst. Würzburg, vii. p. 292 (1885).

generally displayed in selecting worthy local objects, such as museums, improved science schools, and the like. All this of course is admirable and entirely to be applauded, but believing as we do that there is a possibility of the Imperial Institute, if properly conducted, doing more good for the future development of science and commerce in Greater Britain than any other single

organisation can possibly effect, we hope that it will not be starved in favour of merely local objects. We hear that the women of England have already subscribed a noble sum. This no doubt Her Majesty will hand over to the Institute, if it is organised so as to command the confidence and respect of the various leaders of opinion in this country and in the colonies.

MANY of our readers will attach much importance to Colonel Donnelly's letter, which appears in another column. A large increase in the number of students anxious to enter the Normal School of Science and Royal School of Mines was of course to

be expected, and we are glad that this influx has induced the department to take steps to increase the accommodation, and at the same time to insist upon one of the best possible forms of entrance examination; a strict inquiry, namely, into the educational history of each candidate for admission.

THE Norwegian Government has presented a Bill to the Storthing for fixing a standard time for the whole of Norway. The standard time proposed is Greenwich time plus one hour.

MR. W. BALDWIN SPENCER, Fellow of Lincoln College, Oxford, has been appointed to the Chair of Biology in the University of Melbourne, and will leave England in about three weeks. Mr. Spencer distinguished himself lately by his important memoir on the pineal eye in lizards.

A NUMBER of eminent men of science have addressed a memorial to the President, Vice-Presidents, and Council of the Royal College of Surgeons of England, suggesting that the legacy bequeathed to the College by the late Sir Erasmus Wilson might with advantage be devoted to the establishment of an institution having for its object "physiological and pathological research." It is pointed out that the want of such an institution in England has long been felt, and more especially of

late, when we have had to look to Berlin for information respecting tubercle, and to Paris for experiments on the prevention of hydrophobia. That the Government will do anything in the matter no one is so sanguine as to believe; and it is hardly more probable that the want will ever be supplied by public subscription. There is, therefore, much to be said for the present proposal, and the authorities of the College of Surgeons will, no doubt, give it due attention. It seems strange that in London there should be nothing like the splendid laboratories which exist not only in the capital cities of Europe, but in comparatively small German towns, such as Bonn, Strasburg, and Leipzig.

UNIVERSITY COLLEGE, Liverpool, has reason to congratulate itself on having some remarkably generous and enlightened friends. On Tuesday last it was announced at a meeting of the College Council that Mr. Thomas Harrison, shipowner, of Liverpool, had endowed the Chair of Engineering with 10,000/. Only a few weeks ago Sir Andrew Walker, also a citizen of Liverpool, gave 15,000%. to build Engineering Laboratories.

ON Thursday last the honorary freedom of the City of London was conferred upon Mr. H. M. Stanley, in recognition of his services as a traveller and explorer in Africa. The presentation was made at a special meeting of the Court of Common Council in the new council chamber at the Guildhall. The City Chamberlain, in making the presentation, referred to "the remarkable development of journalistic enterprise during the Victorian era," observing that Mr. Stanley was the first member of "the

class of special travelling and war correspondents" whom the City had enrolled among its freemen. Mr. Stanley was evidently much pleased by the honour done to him, and declared that it would stimulate him to further exertions. After luncheon at the Mansion House, he spoke of the various routes which have been proposed for the expedition for the relief of Emin Pasha.

MR. ALFRED RUSSEL WALLACE lately delivered, at Boston, U.S. A., a course of "Lowell Lectures." He proposes to make a Western tour, in the course of which he will lecture on, among other subjects, "The Darwinian Theory: What it is, and How it is Demonstrated," "The Origin and Use of the Colours of Plants," "The Permanence of Oceans, and the Relations of Islands and Continents," and "The Biological History of Continental Islands, Recent and Ancient." Mr. Wallace is thought by the Americans to be a more effective speaker than most of the eminent Englishmen who have lectured in the United States.

THE Indian Survey Staff seems to be considerably undermanned. The Government of the Straits Settlements recently applied to the Government of India for an experienced officer to advise them on the way of placing the system of survey in the colony on a satisfactory footing. As no qualified officer on the former establishment was available, Mr. J. B. N. Hennessey, now on the retired list, was offered the duty, but as he declined it the Straits Settlements Government had to be told that the Government of India could render no assistance on a work so necessary to the development of the colonial resources, and likely to be of so much service to science.

A MOVEMENT is on foot at Gothenburg for the founding of a free University in that city. A large sum of money has already been subscribed.

THE results of the new censuses of France and Germany show a marked falling-off in the rate of increase. In the case of France the rate of increase was low enough before; now it threatens to stop altogether, and in many departments there has been a considerable decrease. The addition to the population in five years has only been 213,857, bringing the total up to 37,885,905. This is equal to an annual rate of only I per cent. per annum. Germany is not quite so bad, but the rate of increase between 1870 and 1880 was abnormally high. The population by the latest returns is 46,844,926 as compared with 45,234,061 five years before; giving an annual rate of increase of 71 per cent. per annum in 1880-85, as compared with 1'14 per cent. per annum in the previous five years.

THE Lieutenant-Governor of the Punjab has proposed to the Government of India the establishment of a University at Allahabad, and has furnished a scheme for such an institution in the capital of his province.

AT the afternoon sitting of the Association for the Improvement of Geometrical Teaching, held at University College, on the 14th inst., the President (R. B. Hayward, F.R.S.) in the chair, the Rev. G. Richardson, of Winchester College, read a paper on the teaching of modern geometry, in which he indicated the lines which, in his opinion, a Syllabus on the subject should follow. The draft, which covered an extent of ground too great, we think, for ordinary school-teaching, did not consist of a bare enumeration of the subjects of sections and chapters, but was rendered very interesting by the quaint humour which lightened up and pervaded the whole. The Rev. J. J. Milne read a short note on a part of the above subject, which had been omitted by the previous speaker, viz. the modern treatment of maxima and minima; his strong point was the light to be derived fron symmetry in the search for cases of maximum and minimum. Mr. G. A. Storey, A. R.A, read a

paper on "Geometry from the Artist's Point of View." In this thewriter introduced Euclid and Apelles in converse, and showed the agreement which exists between the purely geometrical method and perspective. The paper was illustrated by numerous drawings of triangles, squares, and cubes. A brief discussion of the several papers followed, and then Mr. E. M. Langley communicated a very simple proof of Feuerbach's theorem (that the nine-point circle touches the in- and ex-circles of the triangle). We may return to the consideration of one or more of the above papers when they have been printed in the Association's Report. Upwards of twenty new members were elected.

We have received a hand-book entitled "Through the British Empire in Ten Minutes with C. E. Howard Vincent, Esq., С.В., М.Р." It is intended to accompany a wall-map on which Mr. Vincent has brought together a large amount of useful information about the British Possessions. In his hand-book he glances at the leading characteristics of each of the great groups into which the Empire beyond the seas is divided.

A STATE weather-service for Pennyslvania is to be formed at Philadelphia by the Franklin Institute. The State Legislature will be petitioned for an appropriation of 3000 dollars for instruments and publications, and it seems to be assumed that so reasonable a request will be readily granted.

THE Americans also have a Society for Psychical Research. The Society proposes to issue the next number of its Proceedings as soon as sufficient material can be collected. Apparently it is not quite so easy to get startling evidence of the "psychical" kind in the New World as in the Old.

DESCRIBING in an American medical journal the influence of the recent earthquake shocks in Charleston upon the health of the inhabitants, Dr. F. Peyre Porcher, of that city, says that many persons experienced decidedly electrical disturbances, which were repeated upon the successive recurrence of the shocks. These disturbances were generally accompanied by tingling, pricking sensations, like "needles and pins," affecting the lower extremities. One gentleman was completely relieved of his rheumatism; another, who for months was nervous, depressed, and entirely unable to attend to business, regained his former activity and energy.

An interesting sketch of the great Serpent Mound in Ohio is given in Science by Mr. W. H. Holmes. It is in the northern part of Adams County, somewhat remote from frequented routes of travel. The entire body of the serpent and the peculiar features of the enlarged portion are all distinctly traceable, and leave no doubt in the mind, Mr. Holmes thinks, as to their artificial character. He is decidedly of opinion that the work should be classed among the products of the religion of the aboriginal races.

MR. J. H. STEWART LOCKHART, of Hong Kong, has addressed, on behalf of the Folk-Lore Society of England, an appeal in the English and Chinese languages, through the press, to students throughout China to co-operate in investigating the folk-lore of that country. He points out that no attempt has been made to deal with this subject as a whole, the work done so far being for the most part of a local character. He now proposes to obtain collections of the lore peculiar to different parts of the empire and its dependencies. Each collection, he goes on, while in itself highly instructive, will be chiefly important as forming a link in the chain of facts from which a general account of the folk-lore of China may be deduced. The Chinese version of the appeal is intended for circulation amongst natives, who, "experience shows, evince a great interest in the subject when once they comprehend its aims and objects." Competent scholars are scattered over the greater part of China, and, as