700 



STEAM-DIGGER 



M 'DAM-ENGINE 



cost for tear and wear, and for attention in work- 

 ing, than the steam-ploughing gear. The curious 

 circumstance that fewer weeds grow up on land 

 turned over bv the steam-digger than on ploughed 

 land is attributed to the fact that, while the 

 digging forks tear deep-rooted weeds out of the 

 subsoil and Uxw them on the surface, where they 

 are killed by exposure, the plough merely cuts the 

 long roots in two, leaving one portion to seud 

 forth a new crop of weeds. The Darby digger con- 

 cists of a steam-engine with working parts similar 

 to those of an ordinary traction-engine fixed on the 

 top of a double locomotive boiler. The power i- 

 commnnicated by steel spur gearing to a long hori- 

 zontal shaft running parallel with the centre line 

 of the boiler. Thence it is transmitted to the 

 digging-cranks by wheels and pinions of cast steel. 

 There are six digging forks, each about 42 inches 

 wide, so that the digger turns over a breadth of 

 about 21 feet at a time. The digging-forks can be 

 set to work at various depths, down to about 14 

 inches. Whilst digging the digger travels side- 

 ways, and has thus been designated the 'broad- 

 side ' digger. For travelling on the road the travel- 

 ling wheels can be turned HO that it moves like an 

 ordinary traction-engine. When digging it travels 

 at the rate of about half a mile per hour, and allow- 

 ing for turning and stoppages digs over an acre per 

 hour. The cost of this digger with an 8 horse-power 

 engine is 1200, and its inventor claims that it will 

 dig ten acres per day at a net cost of nine shillings 

 per acre, including men's wages, coal, interest on 

 capital and depreciation. The digger invented 

 by Mr Frank Proctor, of Stevenage, consists of 

 an ordinary traction-engine geared into a crank 

 shaft, which works three forks in the rear, so that 

 as the engine travels forward in the usual manner 

 the ground is left dug up behind. These forks can 

 be thrown out of gear or hinged up to permit of 

 the engine being used for threshing or other pur- 

 poses. This system is comparatively cheap, simple, 

 and effective. An 8 horse-power digger costs 800, 

 and in a dav of ten hours should dig ten acres, 

 consuming about 11 cwt. of coal, and requiring the 

 attendance of two men. 



StrailM'llStilH'. Steam-engines in their in- 

 fancy were known as 'fire' (i.e. heat) engines; 

 and in point of fact the older term is the more 

 correct, because the water or steam is only used as 

 a convenient medium through which the form of 

 energy which we call heat is made to perform the 

 required mechanical operations. In modern engines 

 sufficient heat is added to the steam to raise it to a 

 very high pressure, and the excess of this pressure 

 over the pressure opposed to it (either atmospheric 

 pressure or the still lower pressure in a condenser) 

 is both the cause and measure of the work done 

 by the engine. In earlier machines, however, the 

 steam was raised only to atmospheric pressure, and 

 admitted into the engine only to ! at once con- 

 densed by a jet of cold water. The excess of the 

 atmospheric pressure above the pressure in the 

 partial vacuum caused by the condensation was 

 I hen the direct cause of work. Engines of this 

 kind were called <f//m/i/-re engines. 



The invention of steam as a moving power is 

 claimed by various nations ; Inn the first extensive 

 employment of it, mid most of tlie improvements 

 made upon the steam engine, the world indisput- 

 ably owes to Britain and the United States. 



Among the first notices we have in Knglnnd of 

 the idea of employing steam as a profiling force, 

 i- in The Art of Gunnery (1647), by Nat. Nye, 

 mathematician ; in which lie proposes to ' charge a 

 piece of ordnance without gunpowder,' by putting 

 water instead of powder, ramming down an air-tight 

 plug of wood, and then the shot, and applying a 

 fire to the breach ' till it bunt out suddenly. ' But 



the first successful effort was that of the Marquis of 

 Worcester. In his Century of Inventions, the manu- 

 script of which dates from 1655, he describes a 

 steam -apparatus by which he raised a column of 

 water t.> the height of 40 feet. This, under the 

 name of ' Fire-waterwork,' appears actually to have 

 been at work at Vauxhall in 1663-70. Sir Samuel 

 Morland in 1683 submitted to Louis XIV. a pro- 

 ject for raising water by means of steam, accom- 

 panying it with ingenious calculations and tables. 

 The first patent for the application of steam-power 

 to various kinds of machines was taken out in 

 1698 by Captain Savery. In 1(199 he exhibited 

 before the Royal Society a working model of his 

 invention. His engines were the first used to any 

 extent in industrial operations ; they seem to have 

 been employed for some years in the drainage of 

 mines in Cornwall and Devonshire. The essential 

 improvement in them over the older ones was the 

 use of a boiler separate from the vessel in which 

 the steam did its work ; one vessel in all former 

 engines had served both purposes. He made use 

 of the condensation of steam in a close vessel to 

 produce a vacuum, and thus raise the water to a 

 certain height, after which the elasticity of steam 

 pressing upon its surface was made to raise it .still 

 further in a second vessel. 



In all the attempts at pnmping-engines hitherto 

 made, including Savery 's, the steam acted directly 

 upon the water to be moved without any interven- 

 ing part. To Denis Papin (q.v.), a French phys- 

 icist, is due the idea of the piston. It was first 

 used bv him in a model constructed in 1690, where 

 the cylinder was still made to do duty also as a 

 boiler ; but in an improved steam-pump invented 

 about 1700 he used it as a diaphragm floating on 

 the top of the water in a separate vessel, or 

 cylinder, and the steam, by pressing on the top o 

 it, forced the water out of the cylinder at the 

 other end. 



The next great step in advance was made about 

 1705 in the 'atmospheric' engine, conjointly in- 

 vented by Newcomen (q.v.), Cawley, and Savery. 

 This machine (fig. 1) held its own for nearly 



Fig. 1. 



seventy years, and was ^ery largely applied to 

 mines. In it the previous inventions of the separate 

 lioiler and of the cylinder with its movable steam- 

 tight piston are utilised, although in a new form. 

 The "beam,' which has ever since been used in 

 pumping-engines, was used for the first time, and 



