INTRODUCTION. 3 



or labour wliichthe living being- can furnich, may be obtained, 

 it would -put an end to much discussion, and a great deal of 

 conjecture, which is to be regretted. A generation of men 

 would not be condemned to certain military exercises which 

 will be hereafter rejected as useless and ridiculous. One 

 country would not crush its soldiers under an enormous 

 load, while another considers that the best plan is to give 

 them nothing to cany. We should know exactly at what 

 pace an animal does the best service, whether he be required 

 for speed, or for drawing loads ; and we should know what 

 are the conditions of draught best adapted to the utilization 

 of the strength of animals. 



It is in this sense that progress is being made ; but if we 

 complain with reason of its slow advance, we must only 

 blame our imperfect notion of the mechanism of locomotion. 

 Let this study be perfected, and then useful applications of it 

 will soon ensue. 



Man has been manifestly inspired by nature in the con- 

 struction of the machinery of navigation. If the hull of 

 the ship is, as it has been justly described, formed on the 

 model of the aquatic fowl, if the sail has been copied from the 

 wing of the swan inflated by the wind, and the oar from its 

 webbed foot as it strikes the water, these are but a small part 

 of nature's loans to art. More than two hundred years ago, 

 Borelli, studying the stability and displacement of fish, traced 

 the plan of a diving-ship constructed upon the same principle 

 as the formidable Monitors which made their appearance in 

 the recent American war. 



In modern navigation the dynamic question still leaves 

 several points in obscurity. What form should be given to a 

 ship so as to secure its meeting with the least possible resist- 

 ance in the water? What propeller should be chosen in 

 order to utilize the force of the machine to the best advan- 

 tage ? The most competent men in such matters avow that 

 these problems are too complex to admit of the conditions 

 most favourable to the construction of ships being determined 

 by calculation. Must we wait until empiricism, by dint of 

 ruinous guesses, shall have taught us how a problem of 

 which nature offers us such diverse solutions, should be 



