EXPLANATION OF THE PLATES. 48? 



while without the reach of the enemies' guns ; and in the event of being disabled, 

 or at close quarters, twenty short guns of large calibre could be mounted, to offer a 

 proper defence ; and to produce effect when landing troops may be required, she 

 was made to carry on her platform 500 troops. 



In the construction of the Nile, every care was taken to give a suitable degree 

 of strength, and she was built in every respect equal, both in the quality of the 

 materials and in the scantling and dimensions given to her timbers, to any of the 

 armed steam ships heretofore built ; while in the equipment of this vessel, every 

 thing was done that skill and experience could devise or expense accomplish, 

 towards making her as effective as possible. 



The engines of the Nile were by Boulton and Watt: two of 110 horse power 

 each, and which appear to have been most effective, from the manner in which this 

 vessel made her passage out to Alexandria ; and acted when contending against 

 a strong gale and a heavy head sea. From the size of this vessel it might for the 

 sake of velocity have been considered proper to give greater power ; but in deter- 

 mining them, the power given was considered the best suited for making a voyage, 

 when the consumption of fuel must be an object of the first consideration : and the 

 experiment proved, that to accomplish a voyage and to gain the greatest distance 

 in the shortest time, her power was properly proportioned. 



The disposition and particulars of her engines will be best explained by reference 

 to the Plates. 



In determining the elements, and giving the principal dimensions of the Nile, for 

 her construction, the dimensions, &c., of several fast steam vessels were taken to 

 compare with ; but as it was considered of the first importance in the construction 

 of this vessel, that she should be able to carry sufficient sail to keep company with 

 convoys when not steaming, and to make a reserve of her coals whenever practi- 

 cable, it was thought desirable to give a greater breadth than common, so that her 

 length was about 5-5 of her breadth instead of from 5'8 to 6'8, the breadth as given 

 to some of the fast boats ; and the proportion of the area of the load water section 

 to the circumscribing parallelogram formed by the length and breadth was consider- 

 ably more than is commonly given, keeping the area of the greatest transverse 

 section about the same in relation to the circumscribing parallelogram formed by the 

 draught of water and the breadth ; as it was found impossible to reduce this element 

 much, on account of the displacement required being more than common, from the 

 great weights she was intended to carry. Something might have been obtained, as 

 to displacement, and possibly in the area of the midship section, by making the rise 

 of the floor something less ; but in doing this the resistance occasioned by the 

 adhesion of the fluid would have been considerably increased ; probably more than 



