his measures of the friction of engines and of carriages exclude the atmospheric influence entirely-most of his trials with engines being made without velocity, and the others at so slow a rate of motion, that its influence was insensible. By excluding the leading car, he also freed the friction of carriages from its influence. The value of this last, with the cars there used, is accurately 8 lbs. per ton, or of the gross weight. Having instituted frequent comparisons of computed, with the running rates, upon several roads, I find no reason to disparage that result, in any degree, at least with similar cars. Let it however be observed that light cars have less friction per ton than laden cars. The rationale of this is in the compound nature of friction-in the former the resistance is made chiefly at the periphery, where the wheel bears upon the rail-in the other, at the axle-this last, in cars of the usual dimensions, greatly predominating. This may be mentioned among the anomalies of de Pambour's course. SAMUEL ADAMS' COMBINED RIFLE AND SHOT GUN. We have had presented to our notice the above named ingeniously contrived improvement in fire arms. It possesses the grand requisite of all useful improvements in such things-perfect simplicity. The piece when used as a rifle, resembles ordinary arms of that description, and may be loaded as usual, or at the breech by a metallic cartridge. A small piece is unscrewed at the muzzle which loosens the inner or rifle barrel. This is kept in its place by means of an enlargement at the breech in that portion of the barrel in which the metallic cartridge is fitted. The space thus left when the inner barrel is removed, leaves room for a larger metallic cartridge for the shot gun, which may likewise be loaded in both ways. The rifle sight turns on a pivot, and may be put out of the way when the smooth bore is used. The perfect adaptation of all the parts, renders the united barrels quite as firm as if in one entire piece- and as a rifle it is not heavier or as a shot gun, lighter than common arms of those kinds. We consider it as completely supplying the place of two distinct pieces, and combining economy of space and and money. For travellers such a gun would prove invaluable- while the hunter is thus enabled to command game of all descriptions by a single gun. The change may be made in half a minute, from a rifle to a fowling piece. We understand that a small portion of the right is offered for sale, and we conceive it to be a fine investment-being free from the common objection to improvements in fire arms-complication of parts. We are indebted to Mr. Roebling for a communication on the " Theory of the Crank," which came however, too late for this number. It will appear in the next number. BENEFITS OF RAILROADS-We copy the following statement of the performance of a locomotive steam engine on a Pennsylvania railroad. Facts like these are convincing poofs of the superiority of railroads over canals. To this statement we annex some remarks from the Journal of Commerce, elicited by certain articles which have recently appeared in the Railroad Journal on the enlargement of the Erie canal. We profess not to be fully acquainted with this subject, but if the large sum of money necessary to complete this enlargement can be turned to the construction of railroads, we are of opinion a much greater good will be accomplished. Ed. N. Y. Times. UNEXAMPLED PERFORMANCE IN THIS COUNTRY OR EUROPE.-The engine "Gowan & Marx," built by Messrs. Eastwick & Harrison, for the Philadelphia and Reading railroad company, weighing eleven tons, drew yesterday, over the railway from Reading to the Columbia railroad bridge, Peters' Island, one hundred and one loaded cars. Gross weight of train, 423 tons of 2240 lbs. Running time, 5 hours 23 minutes-distance 544 miles, being at an aver age speed of about 10 miles per hour. The coal consumed by the engine in drawing this load was 5600 lbs. or rather less than two and a half tons. The quantity of oil consumed by the whole train of cars was 5 quarts, being about half a gill for each car. The freight was as follows: 2002 barrels of flour, weighing 52 barrels of whiskey, 20 hogsheads of corn meal, whiskey, linseed oil, Lot of band iron, etc., Total nett freight, The following is a statement of the receipt and expense of transporting 423 tons of 2240 lbs., over the Philadelphia and Reading railway. The nett load of 2000 lbs. to the ton was 307 tons or 101 cars. The freight received by bills of parcels was $835 19 for the down tripor $2 78 per ton of 2000 lbs. carried 54 miles in five hours and twentythree minutes. The daily expense of running the locomotive to carry a train one trip. is stated at To this add wear and tear of 101 cars, at the very liberal allowance of 30 cents each per diem, (this rate will renew them every three years.) Add four hands at the brakes, Five and a half quarts of oil, $16 67 30 30 4 2 $52.97 The above does not include the incidental expenses of warehouse and unloading. On the supposition that the cars return empty, it will cost $105 94-it will cost at this rate 35 cents to transport one ton of coal, in a train of cars with 300 tons, 544 miles, between 6 and 7 mills per ton per mile The company calculate to pass daily 2250 tons of coal in fifteen trains with half the above load. This will give them a gross income at $2 per ton on only 708,770 tons, per 315 days, of $1,417,540. The facilities of this road, from its favorable grades, to transport coal, far exceeds the Schuylkill canal along side of which it is located. The capacity of the canal is limited to the number of lockages, during the season of transportation. This period will not usually, on an average, (excluding Sundays, left out on the railroad estimate,) exceed 200 days. If a lockage is allowed every ten minutes, day and night, for the whole season, with the supposition that each boat carries to tide water, on an average, from the mines, 30 tons of coal, we have 744,000 tons, the capacity of the canals. As regards the railway, a train with 200 tons could pass every half hour, say for 315 days, equal to 2,994,000 tons. On a well regulated railway, there would be no difficulty in starting a train every 15 minutes—a railroad with a double track, is nearly equal to travelling in a circle. A POPULAR EXPOSITION OF THE INCORRECTNESS OF THE TARIFFS OF TOLL IN USE ON THE PUBLIC IMPROVEMENTS OF THE UNITED STATES, BY CHARLES ELLET, JR., CIVIL ENGINEER. SECTION 4.-On the most judicious charge on articles of heavy burden and small value. 12. I conceive that it is essential to the fulfilment of the condition, that the tax levied on the trade of the line shall be reconcilable with principles of equity, that the charge at each point shall be proportional to the ability of the article to sustain. And, it fortunately happens, that when the charges are regulated in the mode that will produce the maximum revenue, this condition will be fully satisfied. We are to understand by the ability of a commodity to sustain a charge for carriage, the difference between the cost of production and the market value of the object. If the article be worth $10 in market, and it cost $6 to produce and prepare it for market, it will sustain any charge for transportation, including both freight and toll, not exceeding $4. But its ability to sustain a charge for toll only, depends on the position in which it reaches the line of the improvement. For, after deducting the cost of production from the market value, the residue may go to bear the whole cost of carriage; but we must still deduct from this residue the charge for freight, to obtain the sum which it will bear to be charged for toll. If, for example, the above article reach the line at one hundred miles from the mart, and the freight be one cent per ton per mile, the charge for freight will be $1, and this residue will be $3. If it reach the line at two hundred miles, the charge for freight will be $2, and this residue will be $2. If it come on the work at three hundred miles, the charge will be $3, and the residue will be $1; and if it reaches it at four hundred miles, the freight will be $4, and the residue will be nothing. I say, therefore, that to make the tax for toll proportional to the ability of the commodity, the charge levied by the State for its passage along 100 miles should be proportional to $3, and along four hundred miles it should be allowed to pass free. From which it appears, that the greater the distance the commodity is carried, the less should be the toll levied upon it. In short, I propose that the tax should be proportional to the ability of the trade to sustain the charge; and by such a tariff, to supersede those now in use-by which the tax is increased in proportion as the ability of the trade to bear the tax is diminished. 13. Now, it may be demonstrated, that when the toll is assessed on this principle, both the tonnage and the revenue will be greater than if the most profitable uniform charge per mile that it is possible to levy were adopted. But the method of determining this most productive charge, cannot be conveniently pointed out, with a demonstration of its correctness, in a mere popular discussion. I have, however, elsewhere considered the subject in some detail, and have shown that the toll on this division of the trade which will yield the greatest possible revenue, is about three-eighths of the charge which would exclude the article from market; or three-eighths the limit of the tax which it would bear. In the above example, therefore, the charge at 75 100 miles, should be three-eighths of $3, or $1 12 0 37 00 The difference between these sums and those above given constitutes the profits of the proprietors. It cannot be objected to this scale of charges, that it deprives the citizen on the line, near the mart, of any of the advantages of his position. The work, on the contrary, furnishes him with the means of transporting the products of his estate to a market for one-fourth or one-fifth the sum he was compelled to expend before its construction. This is a positive advantage for which he is indebted to the commonwealth; and he has no right tocomplain, if the same commonwealth extend the benefits of the enterprse to more distant citizens. The avowed object of the improvement is to bring to market productions which could not otherwise reach it, and, generally, to reduce the tax on transportation. And if the objection, that the mode of charging here recommended may seem to disturb the relative advantages of position of the near and distant denizen, be a valid one, it is a fortiori a conclusive argument against all improvement. A consequence of the construction of any canal or railroad, is to increase the value of estates to which it affords new facilities, and of course disturb the relation between the advantages possessed by such property and other estates in the commonwealth, on which it has no effect. But such an objection, even if a legitimate one, cannot be applied to the scale here advised. It is not proposed to tax the distant man less for the transportation of his effects than the nearer one; on the contrary, he is charged more. The method merely proposes to make that portion of the tax which is to be considered as the profit of the State-that portion which is levied for revenue-proportional to the ability of the trade to pay it. And this is justice. In the example given in art. 12, as we have seen above, the toll For 100 miles would be $1 12 200 75 or, actually increasing in proportion to the distance, and at the rate of six and a quarter mills per ton per mile. 14. If, now, we represent by a proper scale, as in Fig. 2, the area of the country which, with the data of this example, would furnish the tonnage, in the hypothesis of an uniform charge of one cent for freight and one cent for toll, we shall have, as before stated, a triangular figure NPN, with a base, NN, of eighty miles, and height, MP, of two hundred miles. But if the charges were adjusted with a view to the obtaining of the maximum revenue, the triangle would have a base, nn, of fifty miles, and a height, MR, of four hundred miles. In the one case the area of the country would be represented by the triangle NPN, and in the other by the triangle nRn. 15. But, instead of aiming to obtain the maximum revenue on all the trade which would reach the improvement from R to M, we may, by the system which it is intended to recommend, adopt in both instances an uniform charge for toll, as one cent per ton per mile, from M to M'-the point which corresponds with the intersection n' of the sides of the superior and inferior triangles-and confine the arrangement made with a view to the maximum revenue, to that portion of the country situated between M' and R. The consequence of this arrangement would be to obtain the same tonnage and revenue from the country traversed by the portion MM' of the line, in both cases, since the tariff would in that distance be common; and at the same time to increase the area of the country trading on the improvement, a quantity equal to whatever would be due to this additional trade and the charge upon it, determined in accordance with the principles here laid down. 16. It will be perceived that the increase of tonnage and revenue which, in the preceding article, is shown to have place, will be obtained without any increase of toll on any part whatever of the trade. We have only to take the present tariff of New York or Pennsylvania, or any other state or company, and obtain these results by a reduction of the charges. For, at the point P, which is supposed to be two hundred miles from M, we have seen that a toll of one cent per ton per mile would entirely exclude the trade. But if instead of a charge of one cent per ton per mile, at that point, or $2 for the entire toll from P toM, the article were taxed but seventy-five cents per ton, as is stated (in article 13) to be the proper toll under the circumstances, there would remain out of the two $2, which is the limit of the charge for toll it would bear at that position, a balance of $1 25 to pay the expense of its transportation from p to P-a distance of twelve and a half miles on each side of the line. So that, by simply reducing the charge resulting from a tariff proportioned to the distance, we shall here obtain, instead of nothing, a revenue due to the tonnage that would be furnished by a district pp, twenty-five miles in breadth, at a charge of seventyfive cents per ton. It is true that a much more important increase of revenue might be experienced by a modification of the uniform charge supposed to be levied from M to M', and a reduction from the new tariff beyond M'. For, even where we adopt the principle of fixing on the determinate toll per ton per mile for a certain distance, we should bear in mind that there is a certain uniform charge which will yield a higher result than any other. But, without any reference to this, or any of the other advantages which would be derived from a thorough and strict regard to the laws of trade in the establishment of the tariff, I have only sought to render clear the fact, that by simple reductions of the charges on a portion of the trade on all our public works, the revenue and tonnage may be simultaneously increased, and the tax on the public may be rendered more equitable. 17. The preceding couclusions are applicable only to the trade in heavy |