EXCAVATING Al Al 'I I INES, for digging and removing earth in extensive excavations, have occupied the attention °finally ingenious men, and various machines for the purpose have been proposed and tried with different degrees of success. The great difficulty seems to consist in adapting any peculiar ‘rrangement of mechanism which shall be capable of digging into the various sorts of earth. Were it only to operate upon a uniform mass, the task would be of comparatively easy accomplishment.
Amongst others who have devoted much time and capita] in the attempt to overcome these difficulties, Mr. G. V. Palmer applied himself to the construction of machines of this kind. lit 1630 he took out a patent " tb• a ina•hine to cut and excavate the earth." This invention is designed, by the applica tion of steam-power, to loosen, dig up, and remove into a cart, earth from a canal or other cavity, and to move itself forwards as the excavation proceeds. lit principle, its leading arrange ment resembles the dredging-machines einploved in clearing the beds of rivers and harbours ; but it has several appurte nances, such as picks, flnr loosening the earth ; for separating it ; and scrapers, fin. filling it into scoops or elevators; the latter convey it into the cart by which it is carried away. The niachinq is 11101nited upon four wheels, and gradually moves forward upon a temporary railway, as the excavation proceeds. The power is applied to the axis of a fly-wheel, and to the same axis is fixed a drum or pulley, around which passes an endless pitched chain. giving motion to another drum or pulley, which revolves in bearings fixed to the upper ends of two long cheeks or this second drum passes another endless Chain, by which a third drum or pulley, of a quadrangular figure, is set in motion, and which turns on an axis in the lower ends of the long cheeks ; to this last-mentioned chain arc :1 series of ea rth-seoups, which are successively brought into operation in taking up the earth. So l'ar, the machine resembles the connnon ballast-enaine ; we have now to describe how the several actions of picking, digging, and projecting the earth are effected. A third endless chain is actuated by the drum on the main axis, and gives motion to a spur-wheel ; this spur-wheel drives another toothed wheel attached to the fore-wheels of the carriage, and thus the carriage gradually advances. By
an ingenious system of levers, connected to a crank on the main axis, a row of pickaxes, a row of cutters, and a row of scraping-shovels. are alternately brought into action. When the pickers have descended and loosened a portion of earth, the cutters tbllow, and separate it from the mass, and this separated portion is immediately afterwards drawn tb• wards by the scraping-sho•els into the scoops, which, by the action of the machine, are brought into the required position on one of the sides of the revolving quadrangular drum ; and filled scoops thence proceeding, to the top of the machine by the revolution of the attached endless chain, discharge their contents into a cart or waggon to be conveyed away. The same gentleman patented another engine for this purpose in 1 83'2. This consisted of an excavated cart and plough united, to be worked by horses or other power. The cart W heels are made considerably wider than those in common use, and the interior portion of the ring of each wheel is made into a series of ea•th-boxes ; these earth-boxes are made to open inwards, and also towards the centres of the Wheels. Underneath the cart, immediately adjoining each wheel, is placed a plough, for raising and turning the earth into the boxes, as the cart is moved lbrwards; the wheels at the same time turning round, bring up the earth, and deliver it into the body of the cart. \Vhen a sufficient load has been thus deposited ill the cart, the ploughs are raised from the ground by means of a lever, and then the cart can be drawn in every respect as a common cart, to the place intended for the deposition of the excavated earth, where it is to be unloaded by withdrawina a pair of bolts. NI hieh allow the bottom or the cart to tbld downwards sufficiently to permit the earth to escape. There are many circumstances where the application of excavating machines of this kind !night be emploviAl to ad' but though the use of them in the X • nNive excavations of railway works has been many tinter aft(1111(ted, they have not been fiuind to answer SO well in practice as to bring them into general enq,loyment.