180 FEATHERING PADDLE-WHEELS. 
curve as could be expected. An error of 1 per cent in the determination of the revo- 
lutions per minute would cause a change indicated by 4 in Figs. 12 and 13, while an 
error of 1 per cent in the determination of the speed would cause the change 
marked B. 
Fig. 15, Plate 98, shows somewhat more clearly than does Table I the relation 
of speed-length ratio and wheel location to the quantity upon which the curves of 
Figs. 10 to 13 have been plotted. 
DISCUSSION. 
Tue CHAIRMAN:—Is there any discussion on this paper on “Feathering Paddle- 
Wheels?” There are some experts on feathering paddles in the Society, I know. I do not 
know whether they are here this afternoon, but one of the greatest is absent, and I am trying 
feebly to take his place. 
I may say that we are always glad to have any discussion submitted in writing, even 
if they are not received here in time to be given before the Society so that we all get the 
benefit of them at the meeting. Naturally, such written discussions as may be sent in will 
be submitted to the author of the paper so that he can take account of them in his sum- 
ming up. 
We are sorry that Professor Bragg is not here, so that he could personally receive the 
thanks of the Society for presenting this paper, which in your behalf I tender to him. 
Proressor BracG (Communicated) :—Mr. Stevenson Taylor has very kindly furnished 
additional data for the City of Erie and Commonwealth, which enables me to add two 
points to each of the curves. 
City of Erie Commonwealth 
ROP OMPURS | oth 6.702 Eerie LACM Van Eas ea 28.4 28 
Speed tiknots., sete erie as aac raed rae eG eae ice, 17.36 OR 
Apparent slip at outside of buckets................... 30.8 29.0 
Displacement ceross) tons eerste 2400 5410 
1 S Meat ean ek iow i Ay Sa A RA a a emp amin IS oe 6 (ber 4600 9050 
These data give points which plot as follows on Figs. 10 to 13, Plates 96 and 97. 
City of Erie Commonwealth 
INDSCiSsa valle ts. ea io eee ele eee ere eee 1.08 2 
Ordinate Fig: 10) poem evenetciers serie: tee nae 0.754 0.76 
Bigs TE iota eae Ree Ryne he Glo cee 0.797 0.844 
AS Teak PAE Aes, Nk Sha Be Sy 5 BMC DIR 1.44 1.61 
Figs) 13) fcc coe ae ee een eR ESA ale 1.52 1.79 
Tue CHAIRMAN :—We will now proceed to paper No. 15, entitled “Alquist Gearing for 
Ship Propulsion,” by Mr. W. L. Emmet. 
Mr. Emmet then presented the paper. 
