114 SURFACE CONDENSERS. 
in use she is 90 per cent of the time at half power, or less, and the other 10 per cent at 
full power, and I wanted the primary condenser to do all of the work when cruising 
at half power and less. No other condenser, so far as I known, has ever been designed 
on this principle. 
In regard to Mr. Robinson’s remarks I discussed this matter with Captain Book- 
walter, engineering manager at our Hog Island plant, and he informed me that during 
this trial we were compelled to use all the auxiliary machinery on board such as the large 
refrigerating and electric light plants in addition to the auxiliary machinery required 
for mere propelling machinery. As a result of this the feed-water heater could not con- 
dense all the auxiliary exhaust and fully 20,000 pounds per hour of this exhaust were 
condensed in the main condenser, making the total figures about 90,000 instead of 70,000 
pounds per hour. 
Furthermore, during this trial we had about ten leaky condenser tubes to contend 
with. With these conditions we were restricted to the use of one air ejector by the trial 
board. Complete data of the trial of May 20 are also furnished as requested (Plate 52). 
In reply to Professor Bragg’s remarks I wish to state that in using a velocity of 
water of 4.37 feet per second I did so on account of the contract requiring 281% inches 
vacuum with 60° sea water; and knowing, if these ships were to be used in other than 
transatlantic service, that sea water of a higher temperature would be used, I left quite 
a margin for the increased amount of water that would be required in order to maintain 
a good vacuum with the higher sea temperatures. A velocity of 6 feet per second is 
very reasonable for a condenser of this design; in fact we are using velocities of 8 and 10 
feet per second with 5<-inch for battleships at the present time. The 988 British thermal 
units are derived from pounds of water per pound of steam multiplied by temperature 
rise, namely, 54 X 18.3 = 988.2. 
Referring to the remarks of Messrs. Orrok and Ricketts I am quite sure, if they will 
look thoroughly into the design of the Tennessee condenser, that they will find it presents 
some fundamentally new features, as no other condenser to my knowledge embodies 
the feature of primary and secondary condensing zones, in which the primary zone 
alone is used for condensing the steam for reduced powers and the secondary zone used 
for air cooling. 
Battleships and the like are subjected to full-speed runs but for a short period, 
so why have a condenser design that condenses all the steam in a portion of the con- 
denser and then let the condensate fall over the balance of the tubes to be further cooled 
by the cold circulating water. 
I thank Mr. Smith for his very kind remarks and the interest shown by him in the 
subject. 
Mr. Kothny has called attention to a typographical error which will be corrected, also 
to the hole in the bottom of the cold air space which was left open for drainage, although 
originally shown with a water seal which would have been better. Regarding the cost 
of these condensers I fully expect the increase in efficiency of my condenser to be more 
than sufficient to pay for the trifling increase in cost many times over. 
In regard to Mr. Morgan’s remarks I think he will have ample opportunity to prove 
for himself any of the doubtful points he refers to as I expect to have him on a trial 
about December 22 of this year on a similar ship to the Cantigny. 
I am not willing to concede Mr. Katzenstein’s remarks on fancy drilling of tube 
