We give a picture, from Black and White. of a picnic party celebrating the opening of a pole railway in the province of Nova Scotia. It is a novel line, thirteen miles in length, and is the third of its kind in the province. For the most part it is utilized in briuging the deposits of silica found in the lakes down the mountains to shipping ports. The way is of spruce poles. The engine has sufficient power to draw four empty cars np the heavy grade of the railway. By taxing the motor to its utmost, and by a liberal use of sand on the rails, eighty excursionists were taken up the incline on the occasion represented. The pole railway is probably the most economical form of steam roadway that has been produced. It is of American origin and bas been in vogue in different parts of the country for the past quarter of a ceutury. It is especially adapted for use ill forest regions, where lumbering is the principal industry. A first class, substantial road built of poles will cost Oi-J anywhere from seventy-five to two hundred and fifty dollars per mile, according to local circumstances. The expense, of course, is greater when the road has to be carried across ravines, as indicated in our engraving. The poles employed for rails should not be less than nine inches in diameter at the smaller end, and should consist as far as possible of the heart, or they will de-cay before they wear out. In the best roads, a bed is hollowed out in the butt end of the pole to receive the small end of the one ad-oining, so as to make a secure junction. The bed is made about nille inches in length and deep enough to permit the smaller end to come up flush with the larger. The poles are simply laid on top of the ground, except when the surface is very uneven, dirt thrown on each side and trampled down to form a solid bed. After they are in place, they areslightly trimmed down with an adz. When a crook of any kind occurs in the poles, it is of course turned down in laying the track. No cross ties are necessary, as the locomotives and cars are so constructed that they exert no lateral preRsure. After a few trains have passed over the road there is no fear of the poles becoming displaced. Curves are made up of a succession of short poles, care being taken that the joints come opposite to each other. The switching is readily accomplished in the ordinary way. Where heavy grades are encountered, it is the practice in some localities to place the locomotive in the middle of the train, and at the particularly steep grades to cut away half the train, push up the other half. uncouple, and return for the remaining cars. In this manner, trains of six loaded car" have been taken over grades of 700 feet to the mile with the use of only one locomotive. The wheels of the cars and locomotives have very broad treads deeply grooved, so as to fit the curvature of the poles. Tile Invisible Spectrum. It is known to a.ll students of sdence that the band of colored light produced by a prism, through which sunlight is passing, appears to stop with dark red rays one way and with deep violet rays in the opposite direction. Much interest has been awakened by attempted study of this color band thought of as going below the visible red end and above the ultra violet. In a recent lecture before the Royal Institution, Dr. William Huggins spoke of these points and the methods of study of them now in use, as follows : " Beyond the violet end of the spectrum there is a whole gamut of invisible rays, which only reveal themselves by their effect in promoting chemical action. Similarly, beyond the other end of the visible scalethe deep redthere is a gamut of invisible or dark rays, which are only perceived by their heating effects. SOllie idea of the importance of the 'ultra red' may be gathered from the fact that it has been traced to a distance nearly ten times as long as the whole range of the visible or light giving region of the spectrum. To learn the character of these mysterious dark rayf,' then, it is clearly necessary for science to fit itself with some new sort of eyes that can see what ordinary eyes cannotnamely, heat rays and chemical rays. The photographic plate has answered admirably as an eye for the chemical rays, and brought out sOllie wonderful facts. But with the invisible heat rays the prohlem was more difficult. Something in the nature of an extremely delicate thermometer is here required, whicb wui pick out all the fine absorption lines ae Solder spots in the spectrum. The beautiful instrument known as the bolometer has recently been used by Professor Langley in feeling for these absorption lines, which, being regions from which the rays are stopped out, are, of course, colder than the remainder of the spectrum. The bolometer, like all the finest applications of science, is an extremely simple thing. It is a strip of fine wire, through which a feeble current of electricity is always flowing. This wire is slowly passed along the invisible gamut of the spectrum, and as soon as it comes to one of the absorption lines the spot is shown by a minute fall of temperature in the wire. This has an instantaneous effect, on the flow of the electrical current. More current will pass through a cool wire than a warmer one, and the alteration is promptly shown by a delicate mirror galvallometer, which flashes its mimic signals onto a slowly revolving photographic ribbon. In this way Professor Langley has been able to pick out and locate hundreds of dark absorption lines in the great invisible spectrum which lies beyond the red. Not only is the absorption of rays by the solar atmosphere shown by this method, but the absorption lines of the earth's atmosphere are equally apparent. Dr. Huggins anticipates that the meteorologist will soon be applying the system to weather forecasts." Nearly all the glass eyes used in the world are made iu Thuringia. Germany. 39 The Rewards or Philosophy. Herbert Spencer's first important work, " Social Statics," was published in 1850, when he was just thirty. The great work of his lifethe " System of Synthetic Philosophy "was taken up in earnest ten years later. The sacrifices involved in the preparation and production of the gigantic work thus heralded to the world were little short of heroic. Those who know Mr. Spencer by his books alone may have thought of him merely as devoting himself to philosophy out of the abundance of his material wealth and comfort. The truth is far otherwise. No man ever lived a more ascetic life or denied himself !!lore for the sake of the task he had undertaken for humanity. In his evidence given before the Commission on Copyright he tells us in plain words, though in the most severely impersonal and abstract manner, the story of his hard and noble fight during the unrecognized days of his early manhood. Not a fight for bread, not a fight for fame, remember, but a fight for truth. For his first book, " Social Statics," in 1850, he could not find a publisher willing to take any risk; so he was obliged to print it at his own cost and sell it on commission. The edition consisted of only seven hundred and fifty copies ; and it took no less than fourteen years to sell. Such are the rewards of serious thought in our generation! Five years later he printed the original form of the ..Principles of Psychology." Again no publisher would undertake the risk, and he published on commission. Once more 750 copies were printed and the sale was very slow. "I gave away a considerable number," says Mr. Spencer pathetically, "and the remainder sold in twelve and a half years." During all that time, we may conclude from the sequel, he not only made nothing out of those two inlportant and valuable books, but was actually kept out of pocket for his capital sunk in them. ,IBefore the initial volume, 'First Principles,'was finished," he observes, ..I found myself still losing. During the issue of the second volume, the -Principles of Biology,' I was still losing. In the middle of the third volume I was losing so much that I found I was frittering away all I possessed. I went back upon my accounts, and discovered that in the course of fifteen years I had lost nearly 1,300adding intereqt, more than 1.200. As I was evidently going on ruining myself, I issued to the subscribers a notice of cessation." He had been living, meanwhile. in "the most economical way possible ;" in spite of which he found he had trenched to that large extent on his very small capital. Spartan fare had not sufficed to make his experiment successful. Nevertheless, he continued to publish, as he himself bravely phrases it. "I may say by accident." Twice before in the course of those fifteen weary years he had been able to persevere, in spite of losses, by bequests of money. On this third occasioIl, just as he was on the very point of discontinuing the production of his great work, property which he inherited came to him in the nick of time to prevent such a catastrophe. Any other man in the wOrld would have invested his money and fought shv in future of the siren of philosophy. Not so Mr. Spencer. To him life is thought. He went courageously on with his forlorn hope in publishing, and it is SOlllecomm consolation to know that he was repaid in the end, though late and ill, for his single-minded devotion. In twenty-four years after he had begun to publish he ha,d retrieved his position, andiwas abreast of his losses. Think of that. you men of business. Twenty-four years of hard mental work for no pay at all, and at the end of it to find yourself just where you started ! Since that time, it is true, Mr. Spencer's works have brought him in, by degrees, a satisfactory revenue; but consider the pluck and determination of the man who could fight so long, in spite of poverty, against such terrible experiences.Review of Reviews. HI No Water Vapor In Mars. As the result of observations made at the observatory on Mount Hamilton. W. W. Campbell came to the conclusion last year that no aqueous vapor is contained in the atmosphere of Mars. This, says Knowledge, is quite a different opinion from that to which Janssen was led by his ob8et'vations, published in 1867, which have been recently rep ublished in the Comptes Rendus. In 1862, Janssen discovered the spectroscopic bands caused by aqueous vapor in our earth's atmosphere, these having been previously observed by Brewster in 1833. From the 12th to the 15th of May, 1867, after having first of all made himself familiar with the bands due to aqueous vapor, he made observations on the summit of Etna. On the 13th the cold was excessive. and the quantity of vapor in the earth's atmosphere was very smallnot enough to make visible the lines in the solar spectrum called group C, and still less group D. When Mars was examined, groups C and D, although feeble, were distinctly visible. It was in consequence of this observation, confirmed later at Palermo and Marseilles, that Janssen announced the presence of the vapor of water in the atmosphere of Mars.