56 ECONOMICAL CARGO SHIPS—SOME MODEL EXPERIMENTS. 
one of the best investments a shipyard could make. These transactions of the principal 
societies, placed in the drawing offices where the draughtsmen could get at them, would 
return too per cent profit every year. 
There is another point I want to make—you men who are connected with the ad- 
ministration of the yards should see to it, for your own benefit, that these results penetrate 
to the men in charge. We know that in many cases the design of the lines is turned over 
to a man who has some whimsical method of design, and it is not uncommon for him to 
spend a great deal of time figuring whether he will put a waterline one-thousandth of an 
inch on this side, going through a point on this station, or one-thousandth of an inch on 
that side going through a point on the next station, when we all know the actual line on 
the ship as built will not come within an inch either way. It would be better to spend 
fifteen minutes getting the proper longitudinal distribution of displacement and then 
draw in the waterlines freehand than to start with a set of lines initially bad in this regard 
and try to improve them by local fairing. 
Pror. C. H. Peasopy, Vice-President:—I am speaking on this paper because it 
refers to Tideman’s coefficients, which are frequently used with profit. I have no ob- 
jection to urge against them if anyone finds it convenient, but I find works on naval 
architecture frequently refer to his coefficients as though they were obtained by him 
originally. I myself supposed that to be the case until one time a Dutch engineer visited 
our place and most kindly sent to us Tideman’s work, which is a very large and im- 
portant volume in Dutch. Fortunately, we had a well-informed Dutchman at the in- 
stitute, who, though not familiar with naval architecture, could at any rate read this 
work to me, and in it it said positively he did not make any tests. There are many people 
who think his results were original, but he states positively in that book that his results 
are derived from Froude’s work. I have many times wondered at Froude’s courage in 
undertaking his work on friction and also why other people have not a like courage and 
give us more modern values. 
Pror. LAWRENCE B. CuapMan, Member:—I think the writer of this paper is to be 
congratulated, as Professor Peabody has congratulated him, on the excellent material 
he has given to the profession of naval architecture. It is rather unfortunate that 
powering data are presented in so many different ways. First we have Taylor’s method 
V 
VL 
method of circular C against circular P, and then Semple comes out with a circular C 
and then Baker’s 
of plotting, which is residuary resistance in pounds per ton against 
; : " : 4 V 
against circular L, and now Mr. Robertson’s paper comes with circular C against VE 
As Mr. Rigg says, Mr. Robertson has taken a good deal of the terror out of the circu- 
lar P by taking the prismatic coefficient out of the radical, and it is a big advance. 
It is easy enough to use all these methods, and at Lehigh we make the students use 
them all. They at least know how to handle them when they get through. It seems to 
me, from what experience I have had, that the Taylor method of plotting resistance on 
speed lengths against pounds per ton is the easiest method. You do not have to get the 
horse-power of the ship to make a comparison with other models, but in the other methods 
you must work up the horse-power before you can make a comparsion. 
