LOWELL, MASS., May 30th, 1853. To the Editor ot the Scientific American : I noticed in a late number of your pape you have made an allusion to a statemen ms-de by me in the " Railway Times," where in I say that " an engine destroys itself at th rate of $10 per day, when in full use." will give you the evidence upon which th " The first cost of the New ork and Eri engines is from $7,500 to $10,500, (not fron 3,500 to $7,500 as given by you.) The ave rage cost is $9,000 instead of $5,000. Th Erie engines run 2,389,271 miles, by the re port for the official year of 1802, and the ex pense of engine repairs was $203,312 48, o eight and a-half cents per mile run. Now b; the time an engine has been in fall use fo twelve years, its first cost and renewals hav so depreciated from wear and age, that i sale would not realize half its original cos when new. The first cost being $9,000, an the repairs having amounted to $25,000 (fo 300,000 miles run at 8 1-2 cents per mile gives $30,000, as the total depreciation o the engine, or $10 per day for 100 miles dail trip. The expense for repairs, as cited by me a five cents per mile, refers to the engines o the Baltimore and Ohio Railway, where wit the use of the patent chilled slip tire fo drivers, they are enabled to save $30,0C yearly in repairs, above what would atten the use of wrought iron tires. You show the depreciation of the Erie en gines, by my statement, to be $426,000 year ly. The valuation of the Erie engines up t the last report, was $1,349,987 29, r.ot allow lowing for any depreciation. If we allow per cent, for annual depreciation, we hav $107,998 98, which added to $203,312 48, th expense for repairs for one year, gives $311 311 46 for the total annual self-destruction o motive power. Were all the engines of th first class dimensions, and in ' full use,' th amount would be increased far beyond you highest estimate of $426,000. As I have furnished you with these facts : detail, I trust you will not consider this a extraordinary statement. ZERAH COLBURN. [The above is from the ' American Rai way Times " of June 2nd, to which Mr. Co burn is a regular and valuable contributor. Change In Locomotive Fuel. A number of experiments have recent been made on the Baltimore and Ohio Rai road by the superintendant for the purpose sting the economy of coke as a fuel in omparison with wood, which has heretofore been used exclusively. The coke made was om the Cumberland bituminous coal, and le result, we understand, has been so satis-actory that it is intended hereafter to dis-ense entirely with the wood. The saving of xpense has been stated to be about 25 per ent. About two years ago the Hudson River ailroad Co. bought a quantity of coke for le purpose of testing its merits comparative-y with wood. We never heard the result, 'he time is not far distant when all our rsil-oads will be compelled to stop using wood or locomotive fuel, and the sooner they set bout preparing lor the change so much the etter. It will be a good thing lor passengers when wood ceases to be used; the spark punishment now inflicted on travellers will then be abolished. As no wood is employed on the English railways, we cannot see how it is that the same fuel used there cannot be used here with equal advantages ; the coke from the Cumberland coal may bring about the desired relief.