Читать книгу Memoirs of the Distinguished Men of Science of Great Britain Living in the Years 1807-8 - William Walker - Страница 15

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Born 1749. Died May 29, 1832.

William Chapman, Civil Engineer, was born at Whitby, in Yorkshire, of a respectable and wealthy family, who had resided in that town for several generations. He inherited the freedom of Newcastle-upon-Tyne from his father, who, in common with all the chief people of Whitby, was engaged in shipping, and was besides particularly distinguished for his attainments in mathematics and other scientific pursuits. William Chapman derived great advantage from his father's knowledge of these subjects, contracting a strong taste for similar occupations. After receiving a liberal education at different public schools, he was put in command, at the early age of eighteen, of a merchant vessel, in which he enjoyed the opportunity of visiting numerous harbours, both in Great Britain and other countries. He continued thus occupied for a period of three years, losing no opportunity of making himself acquainted with the circumstances of the various harbours he was in the habit of visiting, and he thus acquired that valuable practical knowledge on the subject of these works for which he became afterwards so highly distinguished.

After leaving the merchant service, Mr. Chapman was fortunate enough to become acquainted with James Watt, with his partner Matthew Boulton, and also with Mr. Wooller, Engineer to the Board of Ordnance. By these eminent men he was strongly advised to become an engineer, and follow as a profession that which he had already closely studied as an amusement. Chapman accordingly accompanied Mr. Boulton into Ireland, about the close of the year 1783, but although well introduced, was unable to obtain any employment of consequence in that country, until he had written a prize essay on the effects of the river Dodder on the Harbour of Dublin. Shortly after this, he was appointed resident engineer to the County of Kildare Canal, the works of which were carried on under the surveillance of the Duke of Leinster, the county members, and other leading men. In the execution of this undertaking, Mr. Chapman was requested not to alter the direction of the roads intersected by it, although one of them deviated from the right angle across the canal upwards of 50 deg. To meet this difficulty, and knowing that a bridge of the ordinary construction, with any obliquity, could not possibly stand, Chapman invented, and put into practice, the method of building oblique or skew bridges, which has since been so generally adopted throughout the country, in railway, canal, and other bridges. Before this period, (1787), whenever a road crossed the course of a canal or river, requiring the construction of a bridge, it had been usual to deviate the course, either of the road or the object it crossed, so that the crossing should be at right angles; a practice which occasioned a great waste of land and considerable expense as well as awkward and dangerous bends in the roads thus treated. In some few cases where the bridge was required to be of only a small opening, no alteration in the direction was made, but a bridge built of an oblique form, that is with abutments forming oblique angles with the road passing over it, the courses of the arch being built in lines parallel with the abutments, and the ends of the voussoirs bevelled off to coincide with the direction of the road. Bridges built in this manner consequently became highly dangerous when the span was great, or the obliquity considerable. The value of Chapman's invention consists in this, that he gave the means of building bridges on the skew principle, in any required situation, without altering the direction of the roads or wasting material, and at an expense little above that of ordinary rectangular bridges. This he accomplished by the principle of building the courses of voussoirs at right angles to the face of the arch, meeting the abutments at oblique angles, being the very reverse of the system previously practised.

During the progress of the Kildare Canal, Mr. Chapman, at the request of the Duke of Leinster, became overseer, conjointly with him and the Hon. Mr. Ponsonby Moore, for the building a bridge of five arches over the Liffey, to replace the former one which had been carried away by a flood. The bridge itself was a plain structure, but the means employed in forming and securing the foundations attracted general attention, and brought Mr. Chapman into still greater notice. From this time the number and importance of his professional engagements continued to increase, and he was engaged to survey and report upon several projects for the improvement of the navigations of various rivers, of which plans the most important was the navigation of the river Barrow, from Athy downwards. During this period he was appointed consulting engineer to the Grand Canal of Ireland, of which undertaking Mr. Jessop was directing engineer; and under the joint superintendence and surveys of these two gentlemen, the extension of the Grand Canal from Robarts Town to Tullamore was laid out, as well as the Dock between Dublin and Ringsend, and the canal of communication by the line of the circular road. The projected canal from near Tullamore passed through extensive bogs, some of which were thirty feet in depth, and in consequence of its difficulties was laid out by Mr. Chapman himself. The directors of the Grand canal had expended upwards of 100,000l. in a very short space of ground between Robarts Town and Bathangar, from not being acquainted with the extent of the subsidence of bogs under superincumbent weight, or when laid dry by drainage. Mr. Chapman, therefore, availed himself of their dearly bought experience, and adopted the following ingenious method of comparing different kinds of bogs and their relative subsidence. He provided himself with a cylindric implement of steel plate, sharp at the lower edges, and containing exactly one hundredth part of a cubic foot, and having divided the strata of the bogs into as many leading classes and subdivisions as were necessary, he filled the cylinders with a specimen of each, by twisting them round so as to cut the fibres of the bog. The samples thus taken were carefully cut off at the level of the cylindric guage, and their weight having been ascertained, they were left to dry during the space of several months; and when in a firm state and consequently greatly contracted, were again weighed, the result being that the originally wettest bog was found to have lost 10-11ths of its weight, and the firmest 2-3rds, the rest in due progression between. It therefore became a simple process to ascertain pretty nearly the extent of subsidence in any bog to be passed through, and of course to lay out the line of the canal with such levels, that after subsidence, its surface should be at the required depth below the surface of the bog.

Amongst Mr. Chapman's other extensive employments in Ireland, he caused, at the instance of the Irish Government, a survey to be made of the harbour of Dublin to beyond the Bar at Howth; and on this occasion projected a pier from the Clontarf shore to a due distance from the lighthouse, and then to the westward to a proper distance from the north wall, so as to confine all the tidal water covering that vast space, and to cause it to pass down the channel of Pool Beg, in place of being permitted to flow inwards and outwards over the North Bull.

In the year 1794 Mr. Chapman returned from Ireland, and fixed his general residence at Newcastle-upon-Tyne. About this time the great project of a canal communication between the German Ocean and the Irish Sea, was engaging general attention in the North of England, and Mr. Chapman was fixed upon to survey the line of country for this proposed canal between Newcastle and the Solway Firth. His reports on this subject, which were made during the years 1795 and 1796, are still extant; and although the work to which they relate was never executed, the documents connected with it are of a very interesting nature. In 1808 this project, which had lain dormant for many years, was again revived, and Mr. Telford was employed to survey and report upon the best line of canal between Carlisle and a suitable port on the Solway Firth. Although Mr. Telford's plan was highly approved of, the time had not yet arrived for the carrying out of even this small portion of the original great scheme; and it was not until the year 1818, when Mr. Chapman drew up a plan and report upon this line from Carlisle to Bowness, that a Bill was brought into Parliament, for which an act was obtained early in 1819. The canal which has been in successful operation for many years, is eleven-and-a-half miles in length, and cost about 120,000l. It commences on the south-eastern side of Carlisle, and falls into the sea, through a height of seventy feet, by means of nine locks.

About the year 1796 Mr. Chapman became a member of the Society of Civil Engineers, which at that time numbered amongst its members Watt, Jessop, and Rennie, and amongst its honorary associates Sir Joseph Banks, and other leading men of the day. In conjunction with Mr. Rennie, Chapman was then occupied in designing the London Docks, and subsequently the southern dock and basin at Hull. He was also engaged as engineer for the construction of Leith, Scarborough, and Seaham Harbours, the last named work being undertaken for the Marquis of Londonderry.

In addition to his regular professional occupations, Mr. Chapman devoted a portion of his time to the publication of works bearing on engineering. Amongst the most important of these were the following: 'A Treatise on the various inventions for effecting ascents in rivers;' 'Hints on the necessity of Legislative interference for registering the extent of workings in the Coal Seams, and preventing such accidents as arise from want of that knowledge;' 'An Essay on Cordage;' and 'A Treatise on the preservation of Timber from premature decay.' Mr. Chapman also took out a patent for an improvement upon Captain Huddart's system of manufacturing ropes. This method was successfully carried into effect in all the rope grounds on the river Tyne, and in some of those on the Wear and Tweed. His next invention was for an expeditious and easily practicable method of lowering coal waggons, with their contents, immediately over the hatchways of ships, so as to prevent the great breakage of coals which attended the usual method of shooting them through long spouts; this system, after the expiration of the patent became universal upon the Tyne.

Mr. Chapman possessed a robust constitution, and practised through life the most temperate habits; he was thus enabled to retain the full enjoyment of his faculties, and to continue employed upon various public works, in drainages, canals, and harbours, up till within a very short period of his decease, which occurred in 1832, in the eighty-third year of his age.—Life of Chapman. London, John Weale.