150 REPORT— 1866. 



passed each post*. The first 20 feet were intended to enable the model to 

 acquire a uniform speed by the time it arrived at the first jjost. 



A drawing of the apparatus just described was shown at the Birmingham 

 Meeting. 



As the form of model A when half immersed is of itself unstable, it was 

 partly hollowed out, and made stable by the help of leaden ballast. It was 

 found impossible to make satisfactory expeiiments with this model at deep 

 immersions, because it then became too heavy to be trimmed with that de- 

 gree of delicacy which was requisite for the experiments. With model A, 

 therefore, the bow and stern were combined in various ways ; and the under- 

 water experiments were made with model B. This model floated exactly at 

 half the depth when sohd, and with that immersion the experiments were 

 taken as given in the following Tables. It was afterwards hoUowed out, and 

 then loaded to such an extent as just sensibly to tend to sink. Some runs 

 were taken with this model as deep as 15 inches ; and at that time it was to 

 a slight extent hanging on the wire, so as to meet with a little additional 

 friction : these runs are marked with an asterisk. 



WhUc model B was being hollowed out, the run was lengthened to 150 feet, 

 so that iu each subsequent experiment four observations of speed could be 

 made. 



The following Tables show the observations as made when the models were 

 running. 



The first column gives the number of the experiment ; the second column, 

 the weight suspended as before mentioned, plus the weight of the pulley and 

 spindle, the sum being called the " propelling weight." The resistance of the 

 model iu each case was of course approximately oiu-lmlf of this proj)elling 

 weight. 



The third and fourth columns give the times occupied by the model to run 

 thi-ough the first and second spaces of 25 feet each ; the fifth column gives 

 the mean of the two former coliunns ; the next three columns are the three 

 preceding reduced to speed in feet per second ; the next column is the mean 

 of the runs made with the same propelling weight, in feet per second. 



The phenomena that take place at high speeds are described and illustrated 

 by sketches, 



Plate I. 



Plan of the Lake " Fleur de Lis" at Blackheatli, on which the experiments were taken. 

 A is the platform on which the trestle was erected for the propelling weight. Tlie 

 line A B shows the guiding wire. B is the starting point from which the assistant 

 started the models ; and between A and B, parallel with the wh-e and about 9 inches 

 away from it, are placed, at equal intervals, the poles which serve to mark the time of 

 the passhig models. C is the station of a boat, by means of which the assistant com- 

 municates with station B. A vertical section from A to B in this plate is given on 

 Elate III. 



Plate IL 



Contains the body-plan, profile, and waterlmes of Model A. Prom aft, at the height of 

 half the depth, the spindle is seen round which the bow or stem was turned at will, 

 as was reqmi-ed for the experiments. 



Plate III. 



The upper drawing shows the body-plan, profile, and waterlines of Model B. The waterhnes 

 of both models in the bow are pure curves of lines, and in the stem trochoids. The 

 lower diagram on this plate represents a section of the experimental station A B, 

 shown on Plate I. A is a ti-estle erected to carry the propelUng weight, wliich is 

 maintained at the stationary heiglit shown on the diagram ; and the propelling line 

 passes over a pulley near the level of the water. 



* With a stop-watch lent for the purpose by Mr. Frodsham. 



