structure, as represented in Fig. 5. In the typical form of L. sphæricus, on the other hand, the surface is regularly, but faintly reticulated, as shown in Fig. 6. This is most plainly seen in young specimens, but in older examples is often visible on the margins only, while the margins of the valves in the variety favosus are always, as has been said, quite destitute of sculpture. Length one fifty-eighth of an inch.

This form occurred plentifully in some small peaty pools on Eskhause, at an elevation of about 2000 feet. The peculiarities of shell sculpture lead me to suspect that it may be a distinct species, though it must be confessed that in other respects there is little or nothing to distinguish it from L. sphæricus.

EURYCERCUS LAMELLATUS (Müller) is common in all the lowlying lakes, but does not apparently inhabit those of great altitude. The only tarns in which I have found it being Langdale (340 feet) and Easdale (915 feet).

EXPLANATION OF PLATE.

Fig. 1.-Lynceus barbatus, nov. sp., female, x 84.
Fig. 2.-Abdomen of the same, x 210.

Fig. 3.-Lynceus sphæricus, var. favosa, female, x 84.
Fig. 4. Abdomen of the same, X 300.

Fig. 5.-Exuvium of left valve, showing sculpture, x 84.
Fig. 6.-Marginal reticulations of Lynceus sphæricus, x 210.
Fig. 7.-Lynceus globosus, female, x 50.

Fig. 8.-Lynceus elongatus, female, multivalvular form, x 50.

Fig. 9.-Daphnia Jardinii, female, x 25.
Fig. 10.-Abdomen of the same, x 40.

THE PHILOSOPHICAL INSTRUMENTS IN THE PARIS EXHIBITION.

BY C. R. WELD.

AMIDST the vast gathering of products of human industry and invention, which attracted millions of visitors from all countries to the French metropolis this year, the objects classed under the head of Philosophical Instruments hold very high rank. For it is, to a great extent, by the agency of these instruments that the present generation enjoys comforts and luxuries wholly unknown to the early inhabitants of our globe.

While contemplating with feelings of wonder and awe the pyramids of Egypt, we cannot but remember that though they are stupendous monuments of the former rulers of that country, they are also monuments of slavery and drudgery, for by brute force were they heaped up, thousands of toilers and long years being required to do that which now, by the aid of machinery, could be effected in a few months. When the inhabitants of a country are condemned to unceasing labour, progress for the race is impossible. "How," remarks Solomon, thinking probably of the slavery of the nations around him, "shall he that toileth all day long have knowledge," and assuredly the more that we can make machinery perform offices of manual labour, the more will man be raised in the scale of civilization, provided always, that with the leisure thus afforded him, suitable education is provided. For, just in proportion as the exertions of those who toil are aided and systematized by the employment of force-evolving machines, will there result surplus wealth, more and more leisure for all, an educated class spreading wider and lower; in a word, all that is man's proper destiny-progression in happiness.

How greatly machinery is indebted for its perfection to philosophical instruments is well known. Mr. Fairbairn, the eminent engineer, says that when he first went to Manchester, the whole of the machinery required for the mills in Lancashire was made by hand. Now tools, which may be almost regarded as philosophical instruments, so exquisitely accurate and highly scientific is their construction, are employed for this work. The high character of modern British machinery is due to the great pains bestowed on the tools used for its fabrication, a large proportion of which are made by Mr. Whitworth. With the wonderful measuring machine invented by this gentleman, demonstrating the one-millionth of an inch,* and his true plane,

Mr. Whitworth has presented one of these really marvellous machines, and three of his true planes to the South Kensington Museum.

he is enabled to produce tools of an accuracy hitherto unknown, while these in their turn create machinery which has contributed largely to make our country famous and wealthy.

But philosophical instruments embrace a wide range of utility. By their aid we are enabled to explore with safety deep mines pregnant with the fierce fire blast, the astronomer guages the heavens, and guides the mariner over the pathless ocean, and the wonderful phenomena of light, heat, and sound, are examined and made to minister to the wants and comforts of mankind.

The Official Catalogue of the Paris Exhibition enumerates 490 exhibitors of philosophical instruments. At the Exhibition of 1862, the number was 351. Looking at the countries of the former exhibitors, we cannot help being struck by the spread of philosophical science over the globe. For, while the exhibitors of scientific instruments at the International Exhibition of 1862 came, with few exceptions, from well-known countries, several at the Paris Exhibition represented nations which we have hitherto regarded as but semi-civilized.

As astronomical instruments show mechanical progress and invention in their most refined development, we shall commence with them. The instruments of this description by no means represented the high perfection to which their makers have attained. This, however, is not surprising. Astronomical instruments are, as a rule, far too valuable to be sent to an Exhibition. There were, nevertheless, some fine equatorials exhibited.

The largest of these instruments was constructed by Brunner, of Paris, for the Boulik Observatory in Egypt. The object-glass is 8.4 inches in diameter, and it is provided with a very perfect clock movement.

Mr. Dallmeyer also exhibited an excellent six foot equatorial with a 5 inch object-glass. A notable feature of this fine instrument is that the same clock sets two circles in motion, one of which shows sidereal time, while the other moves the telescope. M. Evrard, of Paris, exhibited a large astronomical telescope with a 9.2 inch object-glass, but the performance of this instrument was not equal to that of Mr. Dallmeyer, which on competitive trial was found to be the best refracting telescope in the Exhibition. The superiority of this, and other English astronomical instruments, is partly due to the excellence of the optical glass made by Messrs. Chance, of Birmingham. These gentlemen, and M. C. Feil, of Paris, manufacture the best optical glass.

Reflecting telescopes, which have been highly instrumental in enlarging our acquaintance with the heavenly bodies, and especially with the nebulæ, were very poorly represented. One,

however, exhibited by Secretan, of Paris, was in all respects a most excellent instrument. The chief interest consisted in the speculum, which was one of Foucault's.

Instruments made upon this principle by English artists are so well known to readers of THE INTELLECTUAL OBSErver, that I need not dilate upon their merits, or explain their construction.

The display of mounted and hand telescopes for military, naval, and travelling purposes, was extremely large and excellent. The most important novelty in these instruments was to be seen in those exhibited by T. Ross and Dallmeyer. Their focal length is only from nine to ten times the diameter of the clear aperture; notwithstanding which, they combine excellent definition with great portability. Messrs. Beck exhibited new and very ingeniously constructed binocular telescopes with which some extremely interesting features connected with binocular vision can be examined. A vast variety of binocular operaglasses were exhibited by various makers. The low prices of M. Bardou's small telescopes and opera-glasses considered in connection with their excellence, is astonishing. He manufactures enormous quantities of these instruments for England, where they obtain a ready sale.

France and Prussia made an extremely fine display of altazimuth, meridian circles, and transit instruments. Those exhibited by Brunner of Paris were highly remarkable for combining the great desiderata of lightness and rigidity, and for being applicable either to astronomical or geodisical purposes, both circles being read off by means of micrometer microscopes. The graduation of these instruments was excellent; instead of the figures being cut on brass or silver, they are white on a black ground, and can be read with very great ease.

To no new discovery are philosophical instrument makers more indebted than to aluminium. This light and beautiful metal is peculiarly suited for astronomical instruments. Besides its great lightness, it is extremely rigid, and but little liable to tarnish. Many instruments in the Exhibition were made of this metal, and particularly of bronze aluminium. This is composed of ten parts of ordinary aluminium, and five of copper, and it possesses a strength both vertical and transverse far exceeding that of wrought iron. This metal is especially valuable in the manufacture of sextants, which require to be held in the hand, and often for a long time. Bearing in mind how highly important a part the sextant plays in navigation, it is lamentable how worthless a large proportion of those instruments are. Happily, however, great pains have been lately taken by philosophical instrument makers to improve them, and with considerable success. The show of sextants at the late

Exhibition was excellent. The great desideratum of attaching an effective artificial horizon when the sea-line is obscured, may be said to have been attained. Eminent makers of optical instruments will always supply a good and reliable sextant; but we may observe that no English mariner need now go to sea in doubt respecting the performance of his sextant, as the British Association for the Advancement of Science have organized measures by means of which sextants can be efficiently tested at the Kew Observatory.

The surveying instruments exhibited were greatly superior to those at the Exhibition of 1862. With the theodolite, which is certainly the fittest instrument for measuring terrestrial angles with precision, and which has displaced the separating circle on the continent, very great pains have been taken to obtain precision with compactness. The theodolites exhibited by London, Paris, Berlin, and Vienna makers were admirable, as also were those shown by J. Kern of Aarau in Switzerland, who employs many hundred hands in making these and other instruments. The Industrial Institution of Lisbon also exhibited several wellmade theodolites. A very ingenious stenographic and orthographic machine was exhibited by Cavaliere Rossi of Rome, with which he has made a very trustworthy survey of the catacombs under and around that city. A very good display of telemeters and planimeters was made by France and Prussia, both of which nations have used these instruments extensively in field operations during war.

A very large display by various countries was made of mathematical and drawing instruments. Those exhibited by Elliott Brothers, maintain in all respects the high character of their house. Excellent instruments of this description were also exhibited by Gravet-Tavernier of Paris, J. Kern of Aarau, and Haff of Munich. The extremely low price of the instruments by these makers, as compared with those made in England is very remarkable. The Swiss and Bavarian makers sell a magazine case of excellent instruments containing a beam compass, proportional compass, six pairs of ordinary compasses of various dimensions, several excellent drawing pens, graduated rulers, sectors and protractors, all in electrum metal, for £3 188. The United States of America, which formerly imported nearly all their dividing-engines and mathematical instruments, now manufacture largely and well. The instruments exhibited by Darling, Browne, and Sharpe, of the above country, are admirable. The accuracy of their steel straight-edges is very great, and the divisions on all their scales, which are effected by machinery, are extremely clear and accurate. These articles are manufactured very largely for the engineering establishments of the United States, and also for the English market.