No department of mechanical industry has been subject to more innovations than that of carriage-making, not only in the shape of the body, but also in the arrangement of the wheels, axles, and springs These latter, in particular, have been indefinitely experimen ted upon, and if fixed laws could always be laid down after a series of trials, the form and arrangement of carriage springs would long ago have been a settled fact. That such is not the case it is superfluous to mention, for no springs hitherto made for carriages have com bined the requisite lightness and strength, they being either defective in one or the other, some makers sacrificing strength to lightness, and others vice versa. To attain both these advantages combined is the great desideratum, and we are happy to record the union of these two qualities in a new description of carriage spring invented by M. G. Hubbard, of Roches ter, and which was patented July 22nd,1851. The improvement consists in using a curved bottom and springing a bar around it, which thus adjusts itself to any weight placed upon it. The elastie force of the spring, in this po sition is exerted upon the whole bar, so that, in its operation, the. material is not in the least disorganized nor its properties impaired. An other of the peculiarities of this improvement is the employment of wood for springs, which forms a distinguishing feature of the invention. Every previous attempt of this kind has been unsuccessful from the difficulty of obtain ing suitable 'proportions, and particularly the requisite length, which obstacles have been triumphantly overcome by the inventor. The use of wood for springs appears destined to form an epoch in the history of carriage build ing, and so successful has been its application, that Mr. Hubbardris-- taut to employ them for railroad cars. They can be used for every description of vehicle, however, heavy, and some idea of their strength may be conceived when we state that those intended,1or .stage coaches will require over two tons to bring them down to their bearing, although they weigh less than 50 lbs. They will spring as delicately while carrying passenger as when carrying twenty, and it must be evi dent to any one that in this position they com bine a degree of strength that never can be , used, and durability in proportion to their simplicity and strength. A buggy with these improved springs was exhibited to us by Mr. Lewis, the agent for the patentee, and we can sately say that it exceeds anything ot the kind that we have ever before seen, uniting everything desirable in a carriage. In this opinion we are not singular, for its merits were tried at the New York State Agricultu ral Meeting, in July, when the Committee spoke in the most flattering terms of the im provements, and awarded the patentee their highest premium, which has also been bestow ed at other similar exhlbitions. j For further particulars respecting these new improvements, address M. G. Hubbard, Ro chester, N. Y.