THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



11 



mained stationary. The dredging-vessel was then allowed to drop 

 back with the stream, in order to loosen the bucliet, which, being thus 

 extricated from the incision made in the ground, passes back without 

 resistance. 



The vessel is then hove up to her original position, and the next 

 descending cutters render the previous incision more perfect, and the 

 bucket immediately following these cutters commonly succeeded in 

 tearing up the obstinate mass. Sometimes, however, it happened 

 that the vessel had to be dropped from her work, and hove to it again 

 several times before this effect could be produced. 



These operations, tedious and difficult as they were, succeeded in 

 forming the complete communication between the two lakes in the 

 course of about four months. The distance thus dredged was about 

 300 yards, and the total quantity removed about '20,000 yards. It 

 must, however, be noticed, that the returns of the work done did not 

 exhibit bo large an amount as the above, and this is accounted for by 

 the fact, that a great deal of the material loosened and dislodged by 

 the cutters and buckets was carried down by the stream into deep 

 water, instead of being raised in the buckets to the top of the frame. 

 The excavated earth being in this way as effectually disposed of as if 

 it had all been hauled up by the buckets, it may not appear surprising 

 to learn that the current of the river, although seeming, at first sight, 

 so obviously an obstacle to the process of effective dredging, proved 

 in the way described a great auxiliary to the power of the engine. 



Another instance of the immense advantage which may be derived 

 in some situations from the employment of the dredging engine 

 occurred at the west end of Loch Ness. In this part of its course 

 for a short distance out of the lake the canal runs side by side with 

 the river, which descends from Loch Oich, the summit lake, to Loch 

 Ness. The canal attains the level of Loch Oich by means of six 

 locks, five of which are situate above Fort Augustus, about half a 

 mile from Loch Ness, and the sixth at Kytra, about half way between 

 the two lakes. The locks were founded and carried up beyond the 

 reach of water before the canal was excavated on either side of them ; 

 and here it will be useful to observe the difficulties which would 

 have presented themselves had not the power of dredging been 

 applicable to this work. 



In the first place, any attempt to excavate iu the ordinary way 

 between Loch Ness and the ascending locks would have been 

 immediately followed by a deluge of water from the river, and 

 it was certain, on account of the open and inadhesive nature of the 

 strata between the river and the canal, that the water penetrating into 

 the excavation made fur the latter would have stood at least as high as 

 the level of Loch Ne5s, wh'ch is the lowest drainage it could possibly 

 obtain. Thus the operatio.is of excavating must have been carried on 

 under a depth of twenty feet of water — a case in which manual labour 

 could not possibly be emploj'ed. 



On the other hand the expedient of carrying the canal on a higher 

 level, by building two of the locks immediately at the end of Loch 

 Ness, and in this way obtaining drainage into the lake, would have 

 been attended witli almost equal objections, for the immense coffer- 

 dams which wo\ild have been required in getting do«n tlie foundations 

 in such a situation would have seriously increased both the time and 

 the cost of execution. As it was, however, by means of the dredging 

 engine the canal was easily excavated to its full depth and breadth, 

 from the end of Loch Ness to the tail of the first ascending lock. 



The application of the dredging engine in the case just described 

 leads us to consider one of far greater importance, where a most diffi- 

 cult and extensive work would have been entirely avoided, had the 

 power of the dredging machine been as well known at that time as it 

 has since become. Every history of the Caledonian canal dwells with 

 great minuteness upon the diiEculties experienced in building the sea 

 lock at the eastern end of the canal where it terminates in the Beauly 

 Frith, a part of the Eastern Sea. At this place an embankment was 

 actually carried out into deep water, and after sufficient time had been 

 allowed fur its consolidation, the excavation for the lock was formed in 

 the middle of it. This expedient, ingenious at it certainly was, would 

 have been quite unnecessary if the lock had been built on the solid 

 ground inland, and a passage had been dredged out into deep water. 

 Although it is probable, considering the state of engineering knowledge 

 at that time, that the plan adopted was the best that could then be 

 devised, it is certain that a much better work could have been con- 

 structed in the solid ground before entering the Beauly Frith, and in 

 corroboration of this it may be mentioned, that the sea lock at this day 

 has a considerable dip or inclination towards the sea, an effect no doubt 

 occasioned by the after settlement of the artificial mound in which it 

 was placed. 



With respect to the dredging on the Caledonian canal very little 

 more remains to be said. In various places on the west side of Loch 

 Oich its powers were brought into requisition, but to describe the cir- 



cumstances of its application at length would be merely to repeat what 

 has already been told, witli reference to Locli Doch Four, and Loch 

 Ness. 



Without any disposition to disguise the fact that difficulties serious 

 and annoying occasionally presented themselves, I am quite safe in 

 asserting that in every case a persevering and determined application of 

 tlie dredging engine, in tlie capability of which every one engaged 

 placed the most implicit reliance, succeeded without exception in a com- 

 plete fulfilment of the duties expected and required. As it may be 

 interesting to know the quantities of work performed by the engines on 

 this canal, the following numerical statement may safely be depended 

 on. The total quajitity of dredging on the Caledonian canal exceeded 

 one million of cubic yards, and the engines enriployed were only two in 

 number, a six and a ten-horse power. The former of these was era- 

 ployed in the dredging out of Loch Ness up to the first ascending 

 lock, in which district the quantity dredged amounted to 170,000 

 cubic yards andoccupied eight months. Tiiis engine was also employed 

 in dredging througli tlie slioals of Loch Doch Four, and between this 

 lake and Loch Ness. The ten-horse- power engine was built at Loch 

 Oich, in the year 1816, and was employed in dredging into the lake, 

 through the shallows, and between the summit level and Loch Lochy 

 descending westward. The greatest quantity raised in one day by tlie 

 ten-horse-power engine on the Caledonian canal was 1.300 tons. 



In reviewing the extraordinary performance of the dredging engine 

 in every situation where it has liitherto been employed, it appears to 

 afford "to the engineer means of the most powerful and extensive 

 capability in the construction of a das? of works which must ever hold 

 a place of great importance iu the rank of engineering operations. I 

 allude to docks and harbours, in the construction of which, during late 

 years, the greatest acquirements, both practical and scientific, have been 

 called into action. The well-attested performances of the dredging 

 engine clearly establish the fact that this machine, being set to float in 

 a basin or a channel of water, is capable not only of tearing up and 

 deepening the bed, however hard or solid, but also of cutting away the 

 adjacent land, and extending either the length or breadth of the body 

 of water in any required direction. In the same way the engine would 

 be quite competent, when placed out at sea, to work inland, either to 

 clear out the embouchure of old rivers, docks, or harbours, or, as a still 

 bolder undertaking, to excavate new cliannels where tlie old ones from 

 any cause have been impeded and rendered useless. The design of 

 constructing docks, harbours, and basins of any kind in sheltered situa- 

 tions, at any convenient distance from the sea, may be safely carried 

 into effect, relying on the power of the dredging engine to perfect the 

 communication with the sea, at an expense not exceeding that of 

 ordinar}' excavation. 



To enter into details respecting the cost of dredging in various 

 situations wouW be out of place in a paper of tliis kind, wliich pro- 

 fesses to be a mere outline of its advantages. But I shall at any 

 time feel great pleasure in affording to any individual, or public body, 

 who may think proper to communicate with me on the subject, the 

 benefit of my experience and practical acquaintance from earliest youth, 

 with every particular relating to tlie practice of dredging by steam 

 power. 



4, Acre-lane, West Brixton. THOMAS HUGHES. 



D.xember 15, 1838. 



ON CONSTRUCTION, AND THE USE OF IRON. 



Read before the Architectural Society, on Tuesday, Dec. 4, 1838, by 

 R. E. Philips, Esq., Member. 

 The great end of all the arts is that of making an impression on 

 the imagination and feeling. That imitation of nature frequently does 

 this I believe will be readily admitted ; but that on some occasions it 

 fails, I conceive will also be conceded : the true tests of the arts, 

 therefore, does not rest solely upon the production of a true copy of 

 nature, but whether it answers the end of art, which is to produce a 

 pleasing effect on the mind. Architecture does not rank itself under 

 the banners of an imitative art •, but, like music and poetry, appeals 

 directly to the imagination. There is in architecture an inferior 

 branch of art, in w-hich (he imagination has no concern; it does not 

 lay claim to its appellation as a polite and liberal art from its useful- 

 ness, or as an accessory to our wants and necessities ; but from higher 

 and loftier principles, we are convinced that a man of genius would 

 render it capable of inspiring sentiment, and of filling the mind 

 with great and sublime ideas. The influence of the fine arts upon 

 the intellectual and moral character of a people, their utility and 

 their value, as conferring upon a state iu which they are justly 

 appreciated as the highest proof of civilization, are considerations 

 which cannot be loo much entertained. Persons ai-e too apt to 

 regard the art of design as a mere elegance, as the sign of wealth 



