SCIENTIFIC PROBLEMS OF THE FUTURE. 675 



ship, as compared with the magnitude, period, direction, aud character 

 oi the opposing waves. Nevertheless Mr. White, to whom I again refer 

 as the leading authority, has clearly laid down that a varying percent- 

 age, amounting always to considerably the larger half, of the total 

 resistance to such a vessel's motion through the water is still due to 

 surface or skin friction. 



Broadly, therefore, we are brought to this conclusion, that this friction 

 is the leading and essential cause of the great waste of power in the 

 propulsion of all vessels of man's design, whether partly or wholly sub- 

 merged, when comi>ared with the natural propulsion of fish or marine 

 animals, such as whales, under corresponding circumstances and condi- 

 tions. Hence the question of the i)0ssible reduction of tliis friction is 

 one of vast and supreme importance to the marine engineer. 



Now if we saw that nature solved this problem in only one way, and 

 that way clearly inapplicable to such bodies as steamships, we might 

 well despair of any good result to be obtained by inquiry and investi- 

 gation into the subject. Thus, if all fish, marine animals, and rapidly 

 moving aquatic birds were all alike coated with slime like the eel we 

 might fairly conclude that, as we can hardly hope to coat her Majesy's 

 iiionclads with perpetual slime, we may give the question up. But as 

 a matter of fact we find on a very slight consideration of the subject 

 tUat nature solves this problem in many and various diiferent ways. 

 The slime of the eel whereby, as we may perhaps i^resume, he is enabled 

 to slip easily through the water has no sort or kind of resemblance to 

 the rough, hard, shagreen, or tough outer skin of the shark, nor is this, 

 again, in the least like the scales of the numerous varieties of scale fish, 

 the fur of the otter or the seal, or the feathers of a rapidly diving bird. 

 Here, therefore, as it appears, is a vast field open to inquiry, investiga- 

 tion, and exi)eriment. 



As I think, it is a much more promising field than our present system 

 of piling up enormous engine power to meet an enormous and ever- 

 increasing-resistance. For we have already said that the resistance 

 to our locomotion through water at present increases in a rapidly 

 increasing ratio as we increase the speed; whereas it seems clear that 

 nature in her beautiful arrangements for dispensing with or minimizing 

 skin friction contrives to avoid altogether this disproportionate piling 

 up of resistance to increased speed. It should, however, be noted that 

 this whole problem Is greatly comj)licated by the question of the con- 

 tinual fouling of ships' bottoms, due to the growth of weeds, the shells 

 of marine parasites, etc. Scientific investigators may i)iopose as many 

 elaborate antifriction, surfaces as they please, but any old tar who has 

 seen his shij) frequently coated thickly with barnacles and weeds, in 

 spite of the use of numerous patent antifouling compositions, will be 

 likely to shake his head doubtfully over them. 



This is a serious complication. It means that wc must seek for some 

 substance or some system of construction for the external coating of 



