In No. 17 of the “Scientific American,” I find an article, under the head 'of “ White's Patent Railroad Truck,—A Defence.” I have no wish to engage in controversy with Mr. White or others, but simply to give my opinion on what is stated to be his invention, for when an invention is brought before the public it is open to criticism ; and I must say, after reading his defence, that I am of the same opinion as before, and will endeavor to give reasons for it; in the first place, moving the eccentric cup to one side does transfer the weight ot the locomotive so much to one side of the centre of the truck, by moving the centre pin with the longitudinal groove, which is the centre upon which the truck vibrates in order to accommodate itselt to vertical inequalities in the track, so that whenever this centre is moved to one side, the weight upon two of the journals is greater than upon the other two, and, as I stated before, if moved much to one side, it would tend to cause the result it is meant to avoid. If the centre-pin, about which the eccentric cup is moved, was a part of the saddle, in place of the saddle resting upon it in the groove, then it would be tree from this objection. Mr. White speaks of the loss that might result from faking a locomotive into the shop, in order to move the centre-pin, and the loss that might result in losing a trip in consequence, I will ask if the loss of time would not be much greater in substituting his apparatus in place ot the ordinary centre. Mr. White would have us believe that the success of his truck is in consequence of his movable centre, and he does not tell us that the trucks, for which he substituted his, hxul side bearings, carrying the locomotive upon four, ia place of three points, hence their liability to run off the track upon the Bloss-burgh road, any centre-bearing truck would have answered, and with such his truck ought to be compared, and not with such as are not calculated for even roads. Mr. White speaks of wedges in the pedestals, now the only proper use of such wedges is to adjust the driving axles, so as to get them perfectly at right angles with the cylinder, and to take up any play which may arise from the wear of the boxes and keys, and throwing the axles out of position by the wedges, in order to make the engine track, is like making two wrongs to make one right. The metaphor which Mr. White uses, about its not being prudent to carry five hundred pounds pressure of steam in a locomotive boiler, is strange ; he says, “ but it does not follow that because five hundred lbs. would tend to burst the boiler, that ninety or one hundred pounds may not be used with safety.” It is like saying, well, if it would be unsafe to move the centre much to one side, moving a little wont do any harm ; but allow me to ask if the centre-pin, being out ot place (say one quarter inch), requires so much ma-chinery,must it not be a serious evil ? and the moving the centre to one side, by transferring part of the weight which belonged to the other side, cannot but be objectionable. Mr. White does not say that he is the inventor of centre-bearing trucks; but one might, from his article, presume that he was ; the gentleman to whom he alludes as knowing Mr. Hudson, and his truck (which he never called his) —knows that locomotives with centre-bearings are not new, and that Messrs. Eastwick & Harrison put some locomotives upon the Rochester and Auburn Railroad, having such trucks with eccentric centre-pins for making the engine track, and they were used on the above road several years ago, so that Mr. White's invention is restricted to the peculiar combination of the eccentric cup plate, centre-pin, and saddle, in connection with the centre-bearing truck. From an inspection of the drawings and description of Mr. White's Truck, as exhibited in the “Scientific American,” I think my remarks will be understood, and appear plain to all practical men. It will not be necessary to allude particularly to the extracts of the letters Irom Hiram W. Bostwick, Esq., and W. M. Mallory, as whatfl have eaid applies equally well to their remarks. “ Honor to whom honor is”due,“ is the motto of the ” Scientific American ;“ and permit me to say that I am not actuated by any personal or selfish motive but simply to vindicate the truth. Hoping that this will be satisfactory, I remain, Yours, &c. W. S. HUDSOH. Paterson, N. J , Jan. 10, 1853.