ON STEAM-SHIP PERFORMANCE. 275 



passage," "weight on safety-valves," and "proportion of steam in cylinder," 

 and as a sequence also to the consumption of coal. 



" Time a minimum" shows the hard driving. " Time a constant" shows 

 the si/stem. The relations of " pressure " and " expansion " show how, under 

 hard driving, the highest pressure and the full cylinder produced the highest 

 speed the wind and tide admitted ; or how, the time being a constant, those 

 two elements were varied at the discretion of the commander, within pre- 

 scribed limits, to meet the conditions of wind and tide. 



The result of the system on the coal is a decreasing consumption. 



The Return No. 1 shows the results of certain trials under favourable con- 

 ditions, but in the performance of the daily passage, by four of the vessels, 

 which results are used as the standard tests with which the results of each 

 quarter's returns are compared. 



For example, the 'Scotia' at 15'9 statute miles an hour, consumes 6840 

 lbs. of coal as a standard. (See Table 4.) 



In the Return No. 3, at the speed of 12*96 miles, she consumed 5226 lbs., 

 the first at the rate of 430 lbs. per mile (see Table 5), and the second at 

 about 403. 



Again, in the succeeding quarter the ' Scotia' consumed 7528 lbs. at 14'65 

 miles an hour, or more than .513 lbs. per mile. 



Here was a case for inquiry and explanation. It will be observed that in 

 Return No. 1 the consumption of the 'Scotia' at ordinary work at sea is 

 5820 lbs. per hour; and it is only when the consumption exceeds 6840 lbs. 

 that it becomes a subject of question, the difference between those figures 

 being allowed for contingencies. 



No. 4 (see Tables 12 and 13) is a Return which shows the difference be- 

 tween the issues of coal each half year, and the aggregate of the returns of 

 consumption, the object of which needs no elucidation. 



No. 5 (see Table 14) shows the duration of the boilers, with particulars of 

 the work done. The saving in money under the return system as compared 

 with hard driving was of course very considerable, and the latter was only 

 justifiable as a necessary means of learning the qualities of each vessel, to be 

 afterwards redeemed by the economy oi' the system. 



The ' Hibernia,' it will be seen, was unequal to the service ; and I may 

 here observe, that experience has shown me that in machinery, as in animal 

 power, it is essential that it should be considerably above its ordinary work. 



The want of this extra power was a defect of the early locomotive engines, 

 whose cost of working per mile was very considerably higher than that of 

 the engines now in use. 



This defect, which is that of boiler power, prevails largely in steam-vessels, 

 and especially in the Queen's ships. 



It would be easy to show how system must tend to economy ; and the 

 saving of coal is apparent from the returns, and of course all the engine 

 stores are commensurate. 



But the repairs, the wear and tear, involve a much more important element 

 of economy than even a reduced consumption of coal. 



Now it must be obvious that neither this nor any other attempt to bring 

 an establishment like that at Holyhead under the supervision of a central 

 authority at a distance, could be effectual without a perfect confidence and 

 understanding between the parties. 



This has happily subsisted for some years, and the Superintendent, Captain 

 Hirste, must have the credit of having cordially entered into and faithfully 

 carried out his instructions, for many of which he has furnished suggestions. 



March 8, 1859. C. R. Moorsom. 



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