5. Light for Illumination obtained from the burning of Hydrogen, by M. Gillard.

We have had an opportunity of seeing the successful application of M. Gillard's patent in the extensive silver plate works of Messrs. Christolef in Paris. It is well known that M. Gillard claims the production of a useful light and great heat from the combustion of hydrogen in contact with a coil of platinum wire-the hydrogen being produced by the decomposition of water. The apparatus employed is very simple, and consists essentially of one or more cylinders of iron arranged horizontally in a furnace similar in all respects to the usual ar rangement for the production of coal gas. The retorts are charged with wood-charcoal reduced to small fragments of uniform size and heated to an intense degree. Through each of the retorts steam is conducted in a tube pierced with numerous very minute holes so disposed as to distribute the steam in an uniform and very gradual manner over the heated coal. The boiler for the production of the steam is conveniently situated in the same furnace employed for heating the retorts. Decomposition of water ensues of course, accompanied with the production of carbonic acid, (CO2) carbonic oxyd (CO) in small quantity, of free hydrogen and a limited quantity of light carburetted hydrogen gas, (C2H.) The mixture of these gases is conducted through a lime purifier to remove carbonic acid, and without farther washing or puri fication, the product is ready for use. Consisting almost wholly of hydrogen gas, the flame of its combustion is of course very feebly luminous; to obviate this difficulty, it is burned in contact with a cage or net work of platinum wire gauze surrounding an ordinary argand burner, protected by a glass chimney. This simple contrivance (so well known in the lecture-room) is perfectly successful, and the light given out from gas lamps of this construction is extremely vivid and

constant.

be

This invention claims the following advantages in practice: 1. The gas so produced is cheaper than any other mode of artificial light, costing, as is asserted by M. Gillard and sustained by the ample experi ence of M. Christolef, only about th the average cost of coal gas. 2. The gas has no unpleasant odor, being entirely free from the volatile hydrocarbons which are so peculiarly offensive in oil and coal gas. 3. The products of its combustion are almost solely water, so little carbonic acid resulting in the combustion that practically it may disregarded. 4. This mode of producing gas may be applied to any existing gas works by a slight modification of the retorts, and without any essential change in other portions of the apparatus-the platinum cages being applied to the argand burners. 5. The cheapness of this mode enables us to apply it with great advantage as a fuel for cooking and for numerous purposes in the arts. For example, we saw in the establishment of M. Christolef, the soldering of silver plate accom plished in a rapid and remarkably neat manner by a powerful jet of this gas, driven by a pneumatic apparatus. Its perfect manageableness, the ease with which an intense heat is applied locally and immediately when it is wanted, coupled with advantages of employing for such a purpose so powerful a deoxydizing agent as hydrogen, render this mode

of soldering preferable to every other, and peculiarly suited for the process of autogenous soldering. 6. The nuisances resulting from the presence of large coal gas works in populous districts are entirely avoided by this mode, which is as free from objection as a steam engine. 7. The arrangements are so simple and inexpensive that every establishment where it is desired to employ light and heat, may erect its own apparatus even in the most isolated situation, all the materials em. ployed being every where accessible.

It is understood that M. Gillard has secured his patent in the United States, and it is presumed that his method will soon be practically tested there.

We merely add that the result of M. Gillard's invention in one particular differs from the anticipation of chemists: that is, we should expect from the decomposition of water in this mode the production of carbonic oxyd CO, carbonic acid CO2, and light carburetted hydrogen C2 H, with a limited amount of free hydrogen. The result of his experience, however, seems to establish the statements already made, as may be seen in a report of the Commissioner of the Society for the Encouragement of Industry, &c., to whom the subject was referred.

ART. XXX.-Extracts from the Proceedings of the Twenty-first Meeting of the British Association, held at Ipswich, July 2.*

1. From the Address of Prof. AIRY, the Astronomer Royal, at the opening of the Meeting.

* COMMENCING, then, with the subject which stands first in the Reports of the Association, and on which the funds of the Association have been most generously expended and its influence very energetically employed, I remark that the progress of Astronomy in the last year has been very great. The Earl of Rosse has been much engaged in experiments on the best methods of supporting and using his large mirrors. The construction adopted some time since is still retained; namely, a system of levers distributing their pressures uniformly over eighty-one points, each pressure being transmitted through a small ball which permits to the mirror perfect freedom of slipping in its own plane, so as to take proper bearing in the chain or hoop which supports it edgeways. To Lord Rosse's critical eye the effect even of this mounting, though greatly superior to that of any preceding, is not quite perfect. In the progress of the experiments, some singular results have been obtained as to the set which a metal so hard as Lord Rosse's composition may receive from an equal pressure of very short duration. A surface of silver, I believe, has now been successfully used for the small reflector.

With regard to the character of the discoveries in nebulæ made with this instrument I cannot briefly give any very correct idea. The most remarkable is, the discovery of new instances of spirally-arranged

* From the Athenæum of July 7 and 12, Nos. 1236, 1237.

nebulæ but there are also some striking examples of dark holes in bright matter, dark clefts in bright rays, and resolvability of apparently nebulous matter into stars. I do not deny the importance of the last observation; but as it might be predicted beforehand that the increase in the dimensions of telescopes would lead to more extensive resolution of nebulæ, I do not hold the inference to be by any means certain that all nebulæ are resolvable. Mr. Lassell exhibited at the last meeting of the Association a plan for supporting his two-feet mirrors without flex This plan, slightly modified, has been adopted in use: and I am assured that the improvement in what before seemed almost perfect definition is very great.

ure.

The removal of the vexatious fiscal interferences that have been con nected with the manufacture of glass, and the enterprise with which Mr. Chance as manufacturer and Mr. Simms and Mr. Ross as opticians have taken up the construction of large object-glasses, promise to lead to the most gratifying results. Already Mr. Simms has partially tested object-glasses of 13 inches aperture; and one of 16 inches is waiting not for the flint but for the crown lens. Mr. Ross, it is understood, has ground an object-glass of 2 feet aperture; but it has not been tested. The facility of procuring large object-glasses will undoubtedly lead to the construction of graduated instruments on a larger scale than before; and it is in this view that I contemplate as a matter of no small impor tance, the erection (this year) of the large transit-circle at the Royal Observatory at Greenwich. It is known to many members of the Association that this instrument was constructed in this town, by Messrs. Ransomes & May; and for the admirable proportions of its various parts, for the firmness of fitting of the few portions of which it is com posed, and for the accuracy of the external forms of pivots, &c., it may well be considered as one of the finest specimens of engineering that has ever been produced. As an example of an excellent mechan. ical structure carrying a large object-glass, I think it probable that this Greenwich transit-circle may have a great influence on the construction of future instruments.

I had hoped to be able by this time to report to the Association some account of the American method of recording transits, by a puncture or dot produced by a galvanic agency whose circuit is closed by a touch of the observer's finger,-and especially on its fitness for the wants of a really active observatory; but the delays of construc tion have prevented me from doing so. Shortly before the last meeting of the Association, the President for the time (Dr. Robinson) transmit ted to the government, on the part of the Association, a general request that a large reflecting telescope might be sent to some of the British possessions in the southern hemisphere, for the purpose of observing the southern nebula; and shortly after that meeting an answer was received from the Lords of the Treasury, to the effect that their Lord. ships entirely recognized the importance of the object, but that there appeared to be practical difficulties in the immediate execution of the design. I cannot doubt that when a more explicit plan has been formed, another representation will be accompanied with the same success which has attended every application made by the Association for aid in a carefully arranged design.

The continuation of the observations on a Centauri at the Cape of Good Hope has fully confirmed the result first obtained,—namely, that the parallax of that star exceeds nine-tenths of a second, or that its distance from the sun is about twenty billions of miles. So far as we have the means of judging, this star is our nearest neighbor in the sidereal spaces. The attention of foreign astronomers is still directed to the irregularities in the proper motions of stars, and the opinion seems to be gaining ground that many of them are accompanied by non-luminous companions. In our own solar system, the most remarkable discovery is that (made independently, though on different days, in America and in England) of a dusky ring interior to the wellknown rings of Saturn. It now appears that it had been seen several years before; but it then attracted no attention. How such a ring is composed, and how sustained, are questions upon which perhaps the physical astronomer may long employ himself.

But the discovery for which the year will be most frequently cited is that of three additional planets, included in the same planetary spacebetween Mars and Jupiter-in which eleven others had been previously found. The last of these (Irene) discovered by Mr. Hind, observer in the private observatory of Mr. Bishop, forms the fourth of his list,-and makes his number the greatest that any one man has ever discovered. Some time since, a grant was made by the British government for the perfection of the Lunar Theory and Lunar Tables on which Prof. Hansen, of Gotha, had been engaged, but whose progress was stopped by the interruption of funds in consequence of the unhappy Schleswig-Holstein war. I understand that with the aid of this grant, equally honorable to the British government and to the foreign philosopher, the work is now rapidly advancing. I have reason to believe that the theories of Uranus and Neptune are now undergoing careful revision; and I trust that one of the elements most urgently required, namely, the mass of Neptune, will be supplied from observations of Neptune's satellite made with the large telescopes to which I have alluded.

At the Edinburgh meeting, the attention of the Mathematical and Physical Section was called by M. O. Struve (there present) to the total eclipse of the sun which is to occur on the 28th day of the present month; and the General Committee appointed a committee of members of the Association to draw up suggestions for the observation of the eclipse. These suggestions have been extensively distributed both at home and abroad: and I am happy to announce one of the results. After consideration of the singular appearances observed in the eclipse of 1842, it was determined by the committee to recommend (among other things) that observing stations should be selected, if possible, in triplets: the three stations of each triplet having relation to the north boundary, the centre, and the south boundary of the shadow. The Russian government has fully adopted this suggestion; and has actually equipped six triplets, including in all eighteen stations, with observers and instruments for the observation of the eclipse. Russian officers in the Sea of Azov and the Black Sea will also observe it. Since the issue of the suggestions, the observations made last year on an eclipse visible at Honolulu in the Sandwich Islands have been received; and they make us, if possible, still more desirous that the spirit

of the suggestions should be complied with, as far as possible. There is only one subject of regret connected with this remarkable eclipse,namely, that it will deprive us of the assistance of several astronomers who would undoubtedly have joined this meeting but for the necessity of being ready, at definite points, for the observation of the phenomena. Among subjects related in some measure to astronomy, I may first allude to M. Foucault's experiment on the rotation of the plane of a simple pendulum's vibration; an experiment which has excited very great attention both in France and in England, as visibly proving, if proof were necessary, the rotation of the earth. It is certain that M. Foucault's theory is correct; but it is also certain that careful adjustments, or measures of defect of adjustment, are necessary to justify the deduction of any valid inference. For want of these, the experi• ment has sometimes failed. The Council of the Association have long regretted the very great delay which has occurred in the publication of the geodetic results of our great National Survey; and they were prepared some time since to represent strongly to the government the expediency of taking immediate steps for completing the few calculations which yet remained to be made, and for publishing the whole in a form which should be available for discussions of the figure of the earth. On communicating with the Royal Society, they learned that that body had made an urgent recommendation to the same tenor, and that in consequence, government had consented to place on the estimates a sum of money expressly for the purpose of completing and publishing the scientific portions of the survey. I have received official informa tion that this work is now in active progress; and I cannot but remark on it as a striking instance of how much may be sometimes effected for the purposes of science by simply completing what is nearly com plete. The great Swedish and Russian Arc of Meridian, from the North Cape to the Danube, is so far advanced that its completion is expected in the present year.

At the last meeting of the Association, a Committee was appointed expressly to urge on the government, what had long excited the atten tion of the Association, the defective state of the survey as regards Scotland. I am happy in stating that there is strong reason to hope that a large sum will in future be appropriated to the Scotch Survey.

The next subject to which the influence of the Association was energetically directed is, Terrestrial Magnetism; with which Meteorology has usually been associated. Although the active employment of sev eral of the Colonial Magnetic and Meteorological Observatories has terminated, (those only of Toronto, Hobartown, Cape of Good Hope, Madras and Bombay being retained, and only in partial activity,) the work connected with them has not yet ceased. Much has yet to be done in the printing and discussion of the observations :-a work going on under the care of Col. Sabine. In tacit association with the repre sentative of the government, the agents of the Association are employed at the Kew Observatory, under the superintendence of Mr. Ronalds, in devising or examining new instruments. The Daguerrotype method of self-registration (which is perhaps liable to this objection, that the original records are destroyed) has been extended to the vertical-force instrument. Apparatus has been arranged for the graduation of original