142 



U E D G I N 0. 



PLATE 

 < \xxix. 



Fig.t. 



Windlu*. 

 Kg. 5. 



the chain barrels round, and bring up the gravel ; but 

 in CMC the buckets should take hold too deep in the 

 ground, so as to endanger the breaking of tin- mat -hinc, 

 mew boxes will slip, and thereby prevent tin- i-liain from 

 being broken. Tin- construction of one ot' these boxes 

 is explained more particularly in Fig. 4 : it consists of 

 a cast-iron wheel /, wedged fust on the end of the 

 haft* m H, which U that in the middle of the ship car- 

 rying the 'wheel I. The other wheel, or box k, is cast 

 hollow, OK shewn in the section ; and the first, /, fits 

 into it, being kept in it- place liy two ears o a, screwed 

 on by two bolts. These pressing hard against the rim 

 of the wheel /, causes a considerable friction, which 

 will carry the shaft m round in its fair work, but if 

 over- strained, will slip. n> H', Fig. 2. are levers, which 

 operate upon coupling boxes on the main horizontal 

 shaft, and give the means of disuniting either of the 

 chain barrel* at pleasure, if one of them needs repair, 

 whiUt the other continues its work. The blocks of the 

 pulleys a a, which suspend the great bucket frames, 

 are reeved with a chain, the fall of which passes 

 through the snatch-block r, fixed down upon the deck, 

 anil then winds round the rollers. This is turned by 

 the engine, the axis of it having a worm-wheel / fixed 

 upon it, turned by the worm r, which i* seen t-ndwi-e 

 in the plan, and shewn on a larger scale at Fig 5. This 

 worm is in reality formed upon the inclined spindle L, 

 though it could not be shewn in the true place with- 

 out making a contusion. F.ithcr of the bucket frames 

 can, as before mentioned, be thrown out of gear, or 

 stopped by clutch boxes, to the lever IT IP, Fig. 2. ; and 

 then the lower end being hauled up by the pullcvs 

 a a, till it hangs in a horizontal position, will Ix- very 

 accessible, to repair the chain, or any of the buckets, 

 which frequently meet with injuries from obstacles at 

 tile bottom of the river. 



> 'irtion of The mode of action in this machine is evident from 

 rniidunt. its structure: it is moored in the st rerun by the head or 

 stern, or both, in Rome situations, if it is required to 

 work across the stream. The engine being put in mo- 

 tion, the chain-frames are lowered down, by giving out 

 the chains of the pulleys a a, until the buckets drag 

 -iili.t-iently upon the bottom, to become filled with bal- 

 last in their passage, and come up along the top of the 

 frames, by the motion o:' the chains, till they turn over 

 the upper chain barrels, and discharge their contents 

 into large hoppers or troughs, which are suspended by 

 ropes from the l>eams HH and t" ; and being placed ra- 

 ther inclined, the troughs conduct the gravel into bar- 

 ges, which are moored beneath the extremity of them. 

 Neither of these hoppers, or troughs, are shewn in tlie 

 Plate, as they would tend to confuse the parts of the 

 machine. The motion of each chain is managed by a 

 ingle man : he stands near the end of a long le\cr, 

 which supports the pivots of the worm- wheel /, so that, 

 by moving the end of this lever, the wheel can be dis- 

 engaged from the worm at pleasure, to give it motion, 

 or set it at rest. There is also a gripe, or brake- wheel, 

 not shewn in the Plate, fixed upon the spindle of 

 the roller * ; nnd the gripe is so forcibly grasped upon 

 it by a loaded lever, as to prevent the roller running 

 hack by the weight of the chain frames, even when the 

 wheel < is disengaged from the worm. The wheel / is 

 attached to its spindle only by the friction arising from 

 its fitting on a circular part, so that it is t liberty to slip, 

 if overstrained, without breakini,' the teeth; but 'it is pro- 

 vided w-ith screw*, as shewn in Fig. />. which may be 

 adjusted, to give sufficient friction to raise the load it is 

 required to take up without slipping. 





The attendant has the management of both the levers 

 above-mentioned ; and by means of them, he car. 

 the bucket- to go just as deep as In > t.'.kc up 



the projH-r quantity of ballast ; and a- they deepen the " 



channel, lie gradually eases the gripe- lever, which per- 

 mit* the frame to de-ceiid lower down ; but if at any 

 time the buckets meet with an obstacle, or take such d< i-p 

 hold as to stick fast, (which they will do, without I 1 ' ATI 



stopping the engine, ln>cause of the slipping box, Fig. 

 4-.) he engages the wheel /. with the worm, by means ''* *' 

 of the lever for thi- purpose, and this winds up the chain 

 of the pulleys n ft, till the end of the frame is rai- 

 high from the bottom as to di-cngagc the bucket--, 

 which then rcMime their motion : and the wheel I 

 be immediately cast off from the worm, because it is 

 unnecessary to raise the frame any higher ; but it may. 

 if required, be lowered down to reach the l)ottom again, 

 by relieving the brake-lever. In this manner, the ope- 

 ration proceeds with the greatest safety and dispatch. 

 There are two other rollers similar to I, situated ju-1 

 above the deck, and kept constantly in slow motion by 

 the engine, for the purpose of advancing the engine 

 along in the water. Thus, a strong rope is attach. 

 a mooring block or anchor, placed at -ome di-tance up 

 the stream, mid is passed once or twice round the rol- 

 ler ; then a labourer holds on the end of the rope, in the 

 same manner as is done by a capstan ; and thus the 

 whole engine is slowly brought up, as the channel ii 

 dredged, and constantly advanced to operate upon a 

 fresh part of the bottom. 



The engine is of 16 horse power, and when dredging 

 in a moderate depth, will bring up enough to load tuo 

 barges, :;."> tons each, in an hour, with only three or 

 four men to attend the whole ; and the engine will con- 

 sume about 34-3 Ibs. of Newcastle coals per hour. 



Het'ore concluding this article, we are desirous of re- 

 commending to those who intend to construct barges lor 

 carrying dredging machines, that no expence should be 

 spared in having them buih in the most substantial 

 manner ; lor after tlfe apparatus is erected, the smallest 

 twisting of the barge may be the means of breaking 

 parts of the machinery. Machines on the same gene- 

 ral principle may be erected on any scale, and to dredge 

 in any reasonable depth of water. This depends en- 

 tirely on the length of the bucket frame, which will be 

 found to work hest about an angle of 4 > degrees. \Ve 

 may farther remark, that when it is intended to dredge 

 in shallow water, regard must be had to the construc- 

 tion of the barge, which should be broad and flat, and 

 of a small draught of water, which will give more time 

 to work, as they can only work whilst the bar 

 afloat.' \Ve may also notice, that machines on the fore- 

 going principle work very well with a bucket frame on 

 one side only, which is a considerable saving of ex- 

 pcnce. Upon the whole, these machines are capable 

 of bringing up sand, mud, clay, or gravel ; and even 

 stones of considerable sixe may be taken up, as has 

 been done at Aberdeen, without the smallest risk to the 

 machine, when properly managed, (j. F.) (\v. o.) 



DIM-'.SDKN, Dmnif, DHK8NBM, DiiAznr, I)ii.\7- 

 DoN'Kcii, and l)iusnr\\ and DRESDA in Latin, is the 

 capital of the kingdom of Saxony. It is situated in a 

 rich and fertile country, on the banks of the river F.I be, 

 at its junction with the Weisseritz, and is divided into 

 two parts, called the old and new town, by the first of 

 thc.-c rivers The town properly consists of three 

 parts, Old Dresden, with its three suburbs ; the new- 

 town, (Neu.-tadt,) which received this name from 

 Augustus II. ; and the Frederickstadt or Ostra, which 





