FIELD FORTIFICATION.

Thames Advertiser, Volume XII, Issue 3235, 4 February 1879, Page 3

FIELD FORTIFICATION.

Cam. Small resumed his course of lectures on " Field Fortification " before the Hauraki Engineers on Friday evening last. There waa a good attendance of members of the corps. After a few preliminary remarks, Capt, Small saidln former lectures you have been shown what the Outline and Profile of Fieldworks mean, also the names and properties of angles connected with such works, and several other elementary matters relating especially to earthworks. To imagine that you can remember all that you have been told would, at present, I think, be expecting too much. Before we shall be able to make such progress so as to thoroughly impress the leading features of field fortification upon your minds, it is absolutely necessary that we should have field practice, and we cannot have this until tho required implements are in hand. In this respect I have every reason to believe the Government will shortly supply our wants, without which perforce we must soon come to a standstill, as far as Military Engineering is concerned. I purpose to-night, with the assistance of a number of plans which I have prepared, to give you some further insight into the nomenclature of field works: the selection of an outline, the defence of field works by artillery, and how to defend an unflanked ditch. 7ou are aware that the standard height of an earthwork parapet is 8 feet, and that in accordance with surrounding circumstances its height may be lowered or increased, and that its thickness is calculated upon the estimated weight of the enemy's ordnance, together with the description of earth to be used in its construction. The works may be either open - that is, a portion left without parapet— or enclosed—completely surrounded by parapet-as deemed most advantageous. The name of open works is used for any works open at the rear. Captain Small then, with the assistauce of the black board and a number of diagrams, explained the names and properties of open works, including the Kedan, Lunette, Tenaille, and Tenaille head, double Redan, Queue d'Hironde, Bonnet de Pretre, Hornworks, Crown works, and of enclosed works, redoubts of 4,5, or 6 faces, or circular, the different kinds of star torts, and the bastioned square or pentagonal fort. Captain Small then said a few words about selecting an outline, which was a matter of the greatest importance. The outline should be shaped so as to take every possible advantage of the natural configuration of the ground. The amount of labour necessary, and the time required to construct the work, should also be taken into consideration, not omiting to calculate the space required for the nnmber of men destined for its defence. The rule laid down for an enclosed work is 15 square feet for every man, after deducting the space required for traverses and artillery; a traverse would take about 500 ft., apieca of of parapet

and from 400 to 600 square feet of the terreplein, There should be 1 yard of crest for every two men, and, at this calculation, the banquette should accommodate two thirds of the whole garrison, the remaining third forming a reserve on theterreplein, (Thespeakerhereexpatiafcd on the folly of making a work too small.) When the work is intended for artillery it should be made much stronger than otherwise. Guns may be used to flank a face or ditch, or for the purpose of throwing shot or shell in front of the salients. When intended to fire in one direction holes (called embrasures) are made in the parapet to fire through; if in various directions, the guns are placed on a well-rammed mass of earth, raised to such a height as to enable the gun to be fired over the parapet. This is called "en barbette." It is advisable to place floors of wood for the guns to rest on. To prevent the wheels from sinking in the earth a square piece of timber, called a "hurter," should be placed so as to prevent the wheels from damaging the interior slope, and the platform should have a slope of about 6 inches from the'rear, thus making provision for the recoil. To defend ditches which have no flanking angles a sort of small block house, called a caponier, ss placed under the escarp at its salient, and so the ditch is flanked. A small tunnel, called a gallery, connects the interior with the caponier. Sometimes the plan is adopted of excavating a chamber in the salient of the counterscarp. Oapt. Small then illustrated the above by the aid of several drawings. A number of questions and answers from members of the corps conoluded the lecture.