LoDDER. — On Compound Engines. 147 



The Tables on page 146 will sliow at once the comparative results of the 

 two vsystems in point of economy and speed. Tables A and B are an extract 

 from the ships' log by the chief officer; they show in the first place the average 

 number of hours on the passage each way. 



It will be well to notice a coincidence between Tables A and B in point of 

 time on the down trips. Table A gives an average with the compound 

 engines of 56 hours for the down trips from Auckland to Napier, and 64 '17 

 hours for the up trips from Napier to Auckland — thus making the down trips 

 in twelve per cent. less time than the up trips. 



In working out the averages in Table B, very nearly the same result 

 occurs. The down trips made with the old engines took 56-5 hours, and the 

 up trips 64*7, being twelve per cent, quicker on the down trips, the same as 

 with the compound engines. The result gives for Table A one per cent, in 

 favour of the compound engines in point of speed, taking the average of five 

 months' running. 



Table C shows the consumption of coals with the compound engines for 

 the voyage per hour. ' Table D shows the same for the old engines. 



On comparing C and D we find a saving in fuel of 42*1 per cent, with 

 the compound engines, and this, with the increase of one per cent, in speed, 

 requires for its attainment three per cent, more power. 



This consumption does not include the coals used for banked fires, cooking 

 purposes, or steam winch. I have made the same deductions for Table D as 

 for Table C for these purposes. 



With regard to the general working of these engines up to the present 

 time there is every reason to be satisfied. Certainly there has been one 

 source of annoyance, and thcit has been the excessive priming, actually in 

 some instances taking the w^ater right through the engines into the surface 

 condenser ; but since the addition of another steam dome on the boiler, 

 connecting it with the superheater, the excessive priming has ceased, but the 

 water still rises in the gauge-glass several inches above its true level. I find 

 from inquiries that this is the case, more or less, in all boats using surface 

 condensers, even with low-pressure steam. 



Before going into the various questions that arise with reference to priming, 

 the chemical and electric actions of the steam and water on the boiler, I shall 

 endeavour to show by comparison, theoretically, the superiority of the com- 

 pound principle. I have stated my belief that nearly every screw-steamer on 

 the coast of New Zealand could be similarly converted, and with equally good 

 results. Supposing we take two examples with a similar class of engines, to 

 those in the " Star of the South," but much larger — say one of the steamers 

 now plying on the coast (s.s. "Phoebe"), of which I have been furnished with 

 dimensions of engines, consumption, etc. We have to find from the data 



