To those unacquainted with the locality it is impossible to convey by description any adequate idea of the irregularities of surface which occur in the Sierra Nevada mountains, which are traversed by this line. The tunneling required has been of small extent. The peculiarity of the line is the very extensive employment of trestle bridging, and it is with the view of illustrating this that our engravings have been chosen, Nos. 1, 2, 4, 5, and 6, being examples of trestle bridging, and No. 3 showing a cutting 63 feet deep and 800 feet long through cemented gravel and sand, of the consistency of solid rock, and which is only to be moved by blasting. The trestle bridging has been all constructed as strong-y as possible, and of the best obtainable material. The ties, stringers, and caps are of best quality pine (that from Puget's Sound, nearly equal to oak), and the posts, braces, sills, and piles of red wood. The main posts, 12 inches square, are placed perpendicularly, let into a sill of the same dimensions with mortice and tenon, immediately under the bearing of the track stringers. Outside the main posts, two posts 12 in. by 12 in. extend down, with a run of 1 foot in 3 inches to the sill to which they are tenoned, beside being bolted at the top to the main posts with inch bolts and cast-iron washers. The sills rest on piles on stone foundations. Piles, when used, are driven so as. to come directly under the main posts and braces. The posts are capped with a timber 12 inches square and 9 leet long, into which the posts are tenoned and pinned. Upon the caps rest corbels 12 inches square and 9 feet long, and upon them are laid the stringers, 12 in. by 15 in., secured by iron bolts passing down through them to the corbels. The caps are notched 1 inch to receive the corbels. The cross ties, or sleepers, are securely fastened to the stringers, and upon the sleepers ar" laid the rails in the ordinary manner. The "bents" or frames are placed at intervals of 15 feet from center to center. Trestling thus constructed is said to last from eight to fifteen years. "When necessary it can be renewed at small cost, or filled with earthen embankment by transporting material on cars at far less cost and trouble than would have been incurred in constructing an embankment at first. It now takes three weeks or more to reach San Francisco via Panama, from New York. When the line is complete the journey can be made in seven days, and ultimately, without doubt, in even less time. Prof. Tyndall's Lectures on Light. Prof. Tyndall has commenced a series of lectures on " Light," before the Royal Institution. Their publication will be awaited with eagerness on this side the Atlantic by those who have read his works on heat and sound. His opening address was of a very elementary character, but he introduced a new experiment to prove that the angle of incidence of light is equal to the angle of reflection. A rod of brass, graduated in inches, was supported in a horizontal position, and from its center a thread, drawn tight by a plummet descended into a basin of water, colored with ink in order to get rid of all but surface reflection. A small dimple was necessarily made at the place where the thread entered the ink. A small paraffine lamp was then placed with its flame nearly touching the rod, and at about a yard from the central thread. Upon bringing the eye along the other end of the rod, and watching the small dimple in the water, it was seen to be most brilliantly illuminated when the eye was at the distance of a yard from the center of the rod, thus proving that the angle of incidence is equal to the angle of reflection. To whatever distance the lamp was shifted from the central thread, the eye had to be placed at a similar distance on the other side to get the most brilliant reflection. Blazing Stars. In the year 1866 a star blazed up in the constellation of the Northern Crown, rapidly attaining the second magnitude. It soon began to decline in brightness, falling in twelve days to the eighth magnitude. It was subjected to spectroscopic ob-j servation by William Huggins shortly after it began to fade. This experienced observer was surprised with the phenomenon of two distinct spectra. One of these was the ordinary spect- rum of dark lines, showing the existence of a photosphere of I incandescent solid or liquid matter, inclosed in a vaporous atmosphere. Overlying this was a spectrum consisting of four bright lines. This plainly proved the existence of a second source of light, shown by its peculiar spectrum to be a luminous gas. Two of these lines were the prominent hydrogen lines, and their great brightness showed the gas to be hotter than the photosphere. The conclusion was obvious : the observer beheld a blazing world. A sudden flood of free hydrogen gas had apparently burst from the interior of the star, and was fiercely burning in contact with some other element. The intense heat of this conflagration had also heated the photosphere, so as to render its spectrum more vivid. If, then, the stars are thus liable to become enwrapped in the flames of burning hydrogen, we may speculate as to what would be the fate of the inhabitants of the planets were our sun to emulate the vagaries of its sister orbs and burst out in mighty conflagration.—From " Spectrum Analysis" in Lippin-cott's Magazine for May. Modern and Medieval Architecture. It is a sad truth, that there is something in the solemn a s pect of ancient architecture which, in rebuking frivolity and chastening gaiety, has become at this time literally repulsive to a large majority of the population of Europe. Examine the direction which is taken by all the influences of fortune and fancy, wherever they concern themselves with art, and it will be found that the real, earnest effort of the upper classes of European society is to make every place in the world as much like the Champs Elysees, of Paris, as possible. Wherever the influence of that educated society is felt, the old buildings are relentlessly destroyed; vast hotels like barracks, and rows of high square-windowed dwel lings thrust themselves forward to conceal the hated antiquities of the great cities of France and Italy. Gay promenades, with fountains and statues, prolong themselves along the quays once dedicated to commerce; ball rooms and theaters rise upon the dust of desecrated chapels, and thrust into darkness the humility of domestic life. And when the formal street, in all its pride of perfumery and confectionary has successfully consumed its way through the wrecks of historicalmonu-ments, and consummated its symmetry in the ruin of all that once prompted to reflection or pleaded for regard, the whitened city is praised for its splendor, and the exulting inhabitants for their patriotism — patriotism which consists in insulting their fathers with forgetfulness and surrounding their children with temptation. Is this verily the end at which we aim, and will the mission of the age have been then only accomplished when the last castle has fallen from, our rocks, the last cloisters faded from our valleys, the last streets, in which the dead have dwelt been effaced from our cities, and regener-ed society is left in luxurious posse s s i o n of towns composed only of bright saloons, overlooking gay parterres? If this be indeed our end, yet why must it be so laboriously accomplished? And are there no new countries on the; earth, as yet uncrowned by thorns of cathedral spires, untor-I mented by the consciousness of a past ? Must this little Europe—this corner of our globe, gilded with the blood of old battles, and gray with the temples of old pieties—this narrow piece of the world's pavement, worn down by so I many pilgrims' feet—be utterly swept and garnished for the ! mask of the future ? Is America not wide enough for the I elasticities of our humanity ? Asia not rich enough for its i pride ? or among the quiet meadow lands and solitary hills ! of the old land, is there not yet room enough for the spread-! ings of power or the indulgences of magnificence, without founding all glory upon ruin, and prefacing all progress with I obliteration ?—John Buskin. Simplicity is one of the greatest elements of utility in ma chinery. Complexity should, if possible, be always avoided.