232 SELECTION OF THE BEST KIND OF PROPELLING MACHINERY. 
in several respects to use it generally. Some of the data do not represent the best practice. 
Also, the conclusions which may be drawn from such a table may be in error. 
Furthermore, a comparison of the engine-room machinery only neglects certain factors 
which have an important bearing. Consequently, to obtain a true comparison, it is neces- 
sary to compare values for the complete vessel. 
I agree with the author that the only safe way to determine the best type of machinery 
is to prepare an estimate of net earnings for the particular designs and routes concerned. 
The truth is that, at present, the economic advantage of the Diesel engine over the best 
type of turbine installation in most cases is not great, and rather close figuring is required 
to decide the best type. In such a close comparison, a change in economic conditions may 
reverse the decision. 
There are many cases where the best designs of Diesel machinery have advantages. 
Furthermore, the field of the oil engine is increasing. However, its commercial value would 
be greatly increased by reducing the weight and first cost. 
Mr. Joun L. Bocert, Member:—After what has been said in this discussion and 
thanking Mr. Ackerson for bringing up the subject, I will not take up much of your time. 
I will show you some things by Mr. Ackerson’s own figures. If you turn to Plate 63, 
you will see that he states there that the steamer of 7,800 tons deadweight capacity con- 
sumes for twenty-four hours 34 tons of oil, and that the Diesel ship is put down as using 
11 tons. 
This morning we heard interestingly from Mr. Mallory, shipowner and operator, that he 
could not run a ship on oil down to South America because he could not get oil down there, 
and he had to buy coal at Durban and very poor coal at that. Mr. Ackerson has not given 
the Diesel engine due credit for what it can do on short runs. In a run to Norway the 
captain of a Scandinavian boat, which had an engine of about this size, reported that he sold 
enough oil out of his double bottom in Norway to pay every last cent of cost of fuel for 
his ship. That means something. There is $83,000 put down here, every last cent of which 
belongs to the credit of the motor ship on that run, and the same way in the case of Mr. 
Mallory. 
We may talk about the Hog Island ships. I will not go into anything bigger, because 
they are a drug on our hands—we have so many of them, and some of the speakers on 
standardization put a quietus on ships of this size for many years to come, 
Many of these ships will be changed to Diesel-engine ships, and I will not discuss 
whether they will be a long-stroke engine—with the Diesel engine they will have to have 
at least 54-inch stroke to have 720 feet piston speed, at 80 revolutions, to be first class, or 
whether someone will make them into twin screw. The other answer would be an electric 
motor on the shaft and. Diesel engines in the engine room developing the juice. 
There are two or three good solutions for these methods, but the point I want to bring 
out is this—that on the way to Scandinavia and back it is perfectly possible for a ship that 
can load 1,000 tons of oil in her double bottom to actually travel for nothing, so far as fuel 
goes, and you heard here this morning that it takes as high as 30 per cent for fuel to oper- 
ate a ship. 
You only have 1,000 tons capacity in the bottom of the boats to take care of surplus 
fresh water for your water-tube boilers, and you must have 15 per cent standby in case of 
emergencies, which means it would be 1,173 tons for a thirty-day round trip per steamer. 
