216 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[JlLY 



tare, the Duntlas aqueduct especially, which is situated about 

 4 miles from liatli. 



Tlie number of the works now undertaken prevented the com- 

 nuMicement of new designs, and besides the continental disturb- 

 ;inces began to be seriously felt. From 1795, to the end of tlie 

 century, only four canals were commenced — the Grand Western, 

 tlie Diirnet and Somerset, the Newcastle Junction, and the Aber- 

 i/irn.ihirc. All these, though very useful works, were but of se- 

 rimdary importance. The first-named, running from the Exe to 

 Taunton, cost about 330,000/. — the length is about 35 miles. The 

 ■iecond was never executed; the third is a very trifling affair; and 

 the fourth only goes to the length of 19 miles: 36 canals have 

 lieen commenced in the present century, the principal of which are 

 the Regent's and the Caledonian. The larger undertakings were 

 often abandoned, at least in their chief points, which was the case 

 with the Bridgwater atnl Taunton. The Caledonian, as will be 

 <ei'n, does not pay at all. Tlie Grand Surrey, the original sub- 

 scription for which was 45,000/., but which cost above 300,000/. ad- 

 ditional, pays a very trifling per centage. Tlie Edinburgh and 

 Glasgov, the Macclesfield, and the Grand Union, are the tliree otiier 

 of most importance. Enterprise was, however, busy about the old 

 lines — most of which received important improvements in this 

 period. 



.411 the undertakings here enumerated have been completed by 

 private persons, either singly or in association. The only work 

 actually undertaken by the government has been the Caledonian 

 ( anal. Watt first surveyed this line, but it was carried into exe- 

 cution by Telford. It cuts com])letely through the Scotch islands, 

 ciimmencing at the foot of Ben Nevis, and running through three 

 Scotch lakes to Inverness. The length of the whole is above 

 (iO miles; but very little more than 23 of this is canal, the remain- 

 der being being lakes. The original intention was to facilitate the 

 transport of Baltic timber, but the traffic has turned out far 

 lielow the original expectation. The cost to the government has 

 been above 1,000,000/.; and in 18+2 the expenditure for wages and 

 maintenance actually exceeded the receipts; the former being 

 2,090/., and the latter 2,038/. We must add, indeed, tliat 576/. of 

 the charges are put down as extraordinary expenditure in building 

 boat-houses, &c.; but, even so, the surplus would have been very 

 little more than 500/. There are 28 locks on this canal, of which 

 a chain of eight, called Neptune's Staircase, alone cost 5,000/. 

 The works of the canal are of first-rate order, and the channel of 

 enormous breadtli and depth, as being intended for ship naviga- 

 tion. The width at top is HO feet; at bottom, 50; depth, 20 feet; 

 tlie locks 172 feet by 40. All this explains the cost, together with 

 tlie nature of the country tbrougli which the canal passes; but it 

 is an instance of the failure of government undertakings, as far 

 as mere profit is concerned. Vessels of upwards of 160 tons often 

 pass the canal. — Daily A^ews. 



THE CENTRE OP GRAVITY OF A LOCOMOTIVE 

 ENGINE, 



In all investigations as to the effects produced by the locomotive 

 engine, it is absolutely necessary to determine accurately the po- 

 sition of its centre of gravity. As the ordinar.v method of ascer- 

 taining this point by calculation is both tedious and unsatisfactory, 

 I am induced to give the outlines of a mode which has suggested 

 itself to me, and which, with careful application, will, I find, give 

 an accurate result. The annexed engraving represents' a four- 

 wheeled engine, whose axles are 7 feet from centre to centre. 

 Having first carefully ascertained the total weight of the engine, 

 the weiglit on each pair of wheels must be obtained by repeated 

 trials on a good weighing macliine. Suppose these weiglits are 

 found to lie respectively 11^9 tons, and F^7 tons; the position of 

 a vertical line CC'O, passing through the centre of gravity, can be 



found by the equation jr ="— , where x = distance of the line 



CC'O from /ill ; /= 7 tons, the weight on the front wheels ; d= 7 

 feet, tlie distance lietween tlie axles; and / = 16 tons, or total 

 weight of the engine. 



Having thus found the line CC'O, it must be chalked upon the 

 barrel of the boiler. Assume for a moment that C is the position 

 of the centre of gravity : draw the line C'f. If now the front 

 wheels be placed on the weighing macliiiie, and tlie bind part of 

 the engine raised until the insistent weight indicated is equal to 

 Hi tons, it is evident that the point C will be in a vertical line 

 passing through the points C and/ By suspending two plumb- 



lines in a plane at right angles to the road on which the engine 

 stands, and intersecting the point /, whenever the whole weight of 

 the engine is thrown upon this point, tlie line CC'O will be inter- 

 sected by the plumb-lines in the point C". 



^7 



Could the above method be practically applied, it would be the 

 most simple way of arriving at a knowledge of the point ; but as 

 it would be dangerous both to the engine and machine thus to dis- 

 pose a weight of (in some instances) thirty tons, it has only been 

 mentioned that the following plan may be more readily under- 

 stood : — On an inspection of the figure, it will be seen that the 

 line EQ is equidistant between H and F, and in this line the cen- 

 tre of gravity would have been situated had the weights on H and 

 F been respectively 8 tons. The front wheels having been again 

 placed on the weighing machine, two plumb-lines must be sus- 

 pended as before, but in a plane passing through the line EQ, 

 which may be termed the line of equipoise. It is evident now that 

 if we lift the engine behind, the plumb-lines will intersect the line 

 CC, whenever the weight indicated by the machine is equal to 

 8 tons, and the centre of gravity will be situated in their intersec- 

 tion. In this operation, compensation must be made for that por- 

 tion of the total weight which tends to move the front wheels for- 

 ward. The amount of this force can be easily calculated, but it is 

 better in practice to compensate it by passing the lifting rope 

 round a pulley, so that its direction may be in a right line with the 

 framing of the engine when lifted. 



I have used a four-wheeled engine to exemplify my mode of 



proceeding, because it is the simplest; but a six-wheeled engine 



can be treated in the same way, when the lines CC'O and EQ have 



been found. If h, m, and / represent the weights on the hind, 



middle, and front wheels, and d the distance between h and m, — a 



md 

 point y must be found, by the equation y = — - — , where the 



weights /( and m may supposed to be concentrated: if D be put for 



the distance between y and/ ~ will be the position of the line of 



equipoise. Again, if t be put for the total weight of the engine, 



X ■= — will be the position of CC'O, the vertical line passing 



through the centre of gravity. 



R. M. 



The High Level Bridge on the Tyne, at Newcastle, on the York and Ber- 

 wick line of railway, will, it is expected, he openeii on the 1st of August. The 

 key of the last arch was driven home on the 7ih ult., by the Mayor of 

 Gateshead, Mr. Hawks, of Hawks, Crawshay, and Co., the contractors for 

 the ironwork. The first pile was driven on the 24th of April, 1846, in pre- 

 sence of its designer, Mr. U. Stephenson, M.P. ; and the first segment of 

 the lirst arch was placed so lately as the 10th of July last. The ironwork 

 rising to a height of 120 fett ahuve Ihe bed of the river, much caution was 

 called for, and from the careful and expensive arrangements therefore made, 

 there has been neither loss of life nor limb in the fixing of the six massive 

 arches, many of the castings of which weighed from 10 to 12 tnns each. 

 The cost of the bridge when completed is estimated to be 243,096/. ; the 

 viaduct through Gateshead and Newcastle, 113,057/,; land, compensation, 

 &c., 135,000/. total, 491,153/. 



