42 Mr, E, JekyU [Feb. 16, 



WEEKLY EVENING MEETING, 



Friday, February 16. 



Frederick Pollock, Esq. M.A. in the Chair. 



Edward Jekyll, Esq. M.R.I. 

 On Siege Operations, 



The speaker, after a few preliminary observations, commenced 

 by stating, that it is absolutely necessary for a besieging army 

 thoroughly to invest the place about to be attacked ; that is, 

 simultaneously to occupy positions so as to cut off all communica- 

 tion with the threatened fortress, and to have a numerical force 

 seven or eight times the number of the pent-up garrison. A 

 reconnoissance is then made by the engineers, who, during the 

 first part of the investment, are employed in taking notes of the 

 description of the different fronts of the fortification, in making a 

 correct plan of the work, and the ground in its vicinity ; in which 

 the course of rivers, streams, ravines, and roads, the extent of 

 possible inundations, woods, marshes, or eminences, are accurately 

 laid down. They mark out, with great precision, by means of 

 pickets, placed in the ground, the prolongation of all the faces of 

 the most prominent works, and the salient angles as well : not only 

 because the latter are the shortest road to the fortress, but because 

 they are also the paths the least exposed to the enemy's fire. 



During this reconnoissance, the besieging army, having en- 

 camped out of range of the guns of the place, send forth large 

 working parties to cut down all the timber and brushwood in the 

 neighbourhood, wherewith to construct the necessary materials for 

 the siege. These consist of gun platforms, timber for the lining 

 and support of mine shafts, galleries, and magazines ; but more 

 particularly for the making of gabions, sap-rollers, and fascines. 



The gabion is a cylindrical basket of wicker work, open at both 

 ends, and of various dimensions, but usually from three to four 

 feet in height, and three feet in diameter. Its use and object 

 being to construct hastily a shot-proof breastwork or parapet, when 

 filled with earth, or to line the approaches and batteries when the 

 soil is of a loose and crumbling nature. 



The sap-roller consists of two concentric gabions, placed one 

 within the other, each six feet long, the interval between them 

 being stuffed with logs of hard wood ; the whole mass far exceeding 



