392 KEPORT— 1892. 



have spoken of and sketched roughly the usual character of the curves. 

 Of course, this must depend in some measure on the ratio of the vertical 

 and horizontal scales to one another, and I think you would do good 

 service if you pointed out the desirability of some recognised convention 

 as to what this ratio should be for any particular kind of curve. I have 

 myself pressed the importance of this in discussion at the Institution 

 of Naval Architects, but there has been little response. For instance, 

 a stability curve drawn with a ratio in the scales of 1 : 1 is a very 

 different-looking curve from one drawn with a ratio of 4 : 1, and, as 

 will be seen from a comparison of figs. 17 and 18, might be misleading. 



Fig. 18. 



' The literature of curves is, of course, as scattered as the subjects they 

 relate to. The principles of them are dealt with in almost any work on 

 naval architecture, but their special applications are treated of in Rankine's 

 " Shipbuilding, Theoretical and Practical " ; White's " Manual of Naval 

 Architecture " ; Reed " On the Stability of Ships " ; Thearle's " Theoretical 

 Naval Architecture " ; the " Annual of the School of Naval Architecture " ; 

 the " Transactions of the Institution of Naval Architects " ; the "Trans- 

 actions of the Institution of Engineers and Shipbuilders in Scotland " ; the 

 " Transactions of the North-East Coast Institution of Engineers and Ship- 

 buildei's," and " The Proceedings of the British Association," in which 

 some of the late Mr. Froude's most valued papers may be found ; and 

 others too numerous to mention.' 



Mr, Brodie, the head -draughtsman of the Mersey Docks and Harbour 

 Board, informs me that as a regular thing there are plotted in that office 

 (1) ordinary sections of ground, (2) tidal curves, (3) slopes of tidal sur- 

 face in the estuary, (4) discharge of pumps under different heads, and 

 pump performances generally, (5) the stresses in various framed struc- 

 tures, (6) engine performances, showing total power and losses on the 

 hydraulic systems of the docks, (7) a number of matters not directly 

 engineering, such as the amount of cotton discharged on certain quays on 

 certain days of the year, the discharge of the dock dredgers in certain 

 places, the capital values of certain property at certain times, the time 

 worked by the dredgers, and time lost in repairs by bad weather, &c. 



An interesting case of plotting has been largely employed for the 

 work in the estuary of the Mersey, in connection with a new sounding- 

 machine devised by Mr. Sutcliffe, one of the engineers of the Docks 

 and Harbour Board at Liverpool. This apparatus was designed with a 

 view to the carrying on of an extensive system of soundings at and 

 about the river-entrances to the New North Docks at Liverpool, and 

 its use there proving to be so advantageous that it has been matured and 

 modified to meet the general requirements of river and coast work. By 

 its means soundings can be taken very accurately, and with much less 

 labour than is possible by any other existing means. It admits of sound- 



