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 100,000_l._ 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