N0 - 1B -] QUALITA TIVE RESULTS. 75 



then unhooked and put in motion; the maximum resistance was supposed 

 to be equal to that towing-force which was just able to give to the boat 

 the high velocities at which it was not influenced by dead-water. One 

 would, however, obtain higher values of the maximum resistance, if the boat 

 were towed at different, steady speeds, and the corresponding resistance mea- 

 sured. Under the conditions of the experiments, the velocity of the boat- 

 model was rather quickly accelerated, by the constant towing-force, up to the 

 critical speed; and as the changes of resistance take place after the changes 

 of velocity, the resistance was not fully developed even when the boat was al- 

 ready brought beyond that range of velocities, at which it is influenced by 

 dead-water. It will be shown later, that the influence of this circumstance on 

 the determination of the maximum resistance, is rather significant. 



The maximum resistance may, in consequence, be defined in two ways 

 — according to the results of experiments with constant towing-forces, or at 

 steady speeds. Reasons will be given in section D, for the choice actually 

 made. 



Some other observations of various kinds, on the motion of the boat- 

 model and the water around it, will be mentioned as they arise in the dis- 

 cussion. 



C. NUMERICAL RESULTS. 



The following tables form an extract from my experimental journal, which 

 contained accounts of 744 experiments in all. In this extract only such ex- 

 periments are included as are actually used in drawing the resistance-curves, 

 or as are in other respects, of interest. The experiments not recorded here, 

 were' either less instructive or were not satisfactorily performed, and were 

 therefore repeated. 



The different columns give: 



First and second columns, Date of the experiment and its number in 

 the table. 



Third and fourth columns, The specific gravity S -—^ of the salt- 

 water (the bottom layer), and the depth in cm. of the fresh-water layer on top. 



