56 report — 1865. 



shell, principally occurring at the lines of junction of its separate plates. 

 It was in the form of short columns and fungoid masses, on the tops of which 

 the perisoma rested : this outgrowth presented, on microscopical examination, 

 a calcareous network, finer and more loose than the other portions of the 

 shell. The Echinus was not altered in form externally, but it seems pro- 

 bable that such a growth, by uniting the plates composing the shell and so 

 preventing the increase at that part, should ultimately cause some distortion. 



Interim Report of the Committee on the Resistance of Water to Floating 

 and Immersed Bodies. By W. J. Macquorn Rankine,C..E., LL.D., 

 F.R.S., John Scott Russell, C.E., F.R.S., James R. Napier, 

 Marine Engineer, and William Froude, C.E. 



1. The following Interim Report describes the experiments made by the 

 Committee up to the day before the commencement of the present Meeting. 

 Those experiments are still in active progress. 



2. The Committee held several meetings in the course of the past winter 

 and spring, and agreed to a programme of experiments of which the follow- 

 ing is a summary. 



3. Two models to be made of painted wood, designated respectively as A 

 and B. 



The models to be ship-shape, and each of them to consist of two equal 

 and similar halves joined together at the middle water-line. 



Elements of Models. 



A. B. 



Length 4-000 feet 4-000 feet 



Breadth 0-571 foot 0-571 foot 



Total depth 0-571 „ 0-364 „ 



Form of Midship Section. Circle. Ellipse. 



Area of Midship Section 0-256 sq. feet . . . . 0-163 



Form of Water-lines of fore-body Harmonic curves. 



Form of Water-lines of after-body .... Trochoids. 

 Stem and stern-post vertical straight lines. 

 Length of fore-body : Length of after-body ::3:2 ....3:2 



Mean girth 1-45 foot . . 1 foot. 



Model A to be in two parts joined at the circular midship section, so that 

 Toy turning the after-body through a right angle about a longitudinal axis 

 the water-lines can be converted into buttock-lines, and vice versd. 



4. Experiments to be made according to the method formerly put in prac- 

 tice by Mr. Scott Russell, in which the uniformity of the propelling force is 

 maintained by means of a regulating weight hanging from a pulley under 

 which the hauling cord passes ; the model to be guided in a straight course 

 by means of a stretched wire. 



5. Those experiments to be made principally at speeds not exceeding the 

 natural speed of the wave corresponding to the length of the model, viz., about 

 two knots per hour ; but a few experiments may be made at higher speeds. 



6. The experiments to be made on each model under two circumstances, 

 viz. with the model immersed as nearly as may be to the middle water-line, 

 and with the model totally immersed. 



7. The programme of experiments having been thus drawn up by the Com- 

 mittee, the superintendence of its execution was undertaken by Mr. Scott Rus- 

 sell, as being the only Member of the Committee resident in or near London. 



