N. S., of Mass —We understood you to mean, by the double bearing in axlea, u the axle divided and having two eide and two central bearings, like the one patented by R. Stephenso " The double bearings on each side have been in use a considerable time. If the generator was merely claimed for saving the excess of heat not ued, we should not have found any fault. We shall endeavor to give jou th other information soon. G. r. W., of R. I.—If you millreferto the Sci Am. No 34, you will find a description of Gardner's axle, which embraces the same contrivance as yours. H R., of 111.—There is nothing new in your coup ling for cars ; 1he invention is old and well O C, of Ohio—We advtee yau not to expend money upon your Safety R it. Track; it is probably pa-tentabLe. but we think you could notget it in.trodu ced ; several plaos equall as good have "ksen proposed to effect the same object, none of which have been adopted. B. S,, of Oonn.—We cannot tell the power of jour wheel, but if you multiply the quantity ia pounds discharged per minute, by tie perpendicular height and divide that by 33,t00, jou will obtain -the hoise power of the water : one wheel will give asmucha-B 20 per ceat, more than another. S. W. G , of Conn.—We could not tell you the size of bar, for we have never used an electro-magnet capable of raising GOOOlbs. More depends on the manner in which the magnet is made, than the size of the bar : the finer the wire the better the magnet; it will take about 40 cups of a Groves' battery to work the force you rectuire. L. 1?'. H., of Tt.—Your me'hod of hanging a saw without a sash is entirely different from that described in the Sci. Am. to which you refer ; we have never seen an arrangement of the kind you speak of; weseeno reason why youare not entitled to a patent. W R. H., of Wis—Heat oil to as high a degree of heat as possible nithout setting it on fire, dip in your steel squares f or a few minutes, then take them out and dip them in cold water; in this way you will be able to temper them. A. A. H , of N. Y.- -Your arroyi'ment for a clamp has been used quite frequently for other purposes than the one for which you einpioy it; its application for that purpose does not produce a resul t that would enlitleyou to letters patent; you had better not make ti'i application. S. W., of Pa.—No circular railway would be allowed in a i'ark in this city ; a ton weight cannot propel more than a ton weight, and it would all depend on the height the weight had to fall, for velocity ; bodies fill at the rate of 16 feet during the first second ; you could not operate your car on a level by the weight of the passengers G. B , Jr., of Md—Weareafraid you cannot obtain a patent for your composition, as nearly all the substances employed by you have been used by others ; when you come here we will talk over the matter. Money received on account of Patent Office business for the week ending Saturday, July 9 :— W. 1'. T., of N, Y, $25 j J. McC , of N Y., $20 ; P. B. ., of Me.. $55; W. G., Jr., of Ohio. $30 ; L. B. A., of Pa., $25 ; C. D , of 111., $10 ; D. B. M., of N. Y., $30. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday July 9 :— C, D.. of 111; D. H , of Ky.; L. B. A., of Pa ; B. F. H , of 111.; W. V. 1., of N. Y.: J. McC, of N. Y.