59 



eii(Bo\ov on a boat of burden, but I hope some clay to see 

 all our ships of war loaded with bread and wine, instead 

 of artillery.) Then I shade the entire form {c) ; and, 

 lastly, reflect it in the water {d) — and you have seen some- 

 thing like that before, besides a boat, haven't you ? 



There is the gist of the whole business for you, put in 

 very small space ; with these only differences : in a boat, 

 the air strikes the sail ; in a bird, the sail strikes the air : 

 in a boat, the force is lateral, and in a bird downwards ; 

 and it has its sail on both sides. I shall leave you to fol- 

 low out the mechanical problem for yourselves, as far as 

 the mere resolution of force is concerned. My business, 

 as a painter, is only with the exquisite organic weapon 

 that deals with it. 



67. Of which you are now to note farther, that a bird 

 is required to manage his wing so as to obtain two results 

 with one blow : — he has to keep himself up, as well as to 

 get along. 



But observe, he only requires to keep himself up he- 

 caiise he has to get along. The buoyancy might have 

 been given at once, if nature had wanted that only ; she 

 might have blown the feathers up with the hot air of the 

 breath, till the bird rose in air like a cork in water. But 

 it has to Ije, not a buoyant cork, but a buoyant hullet. 

 And therefore that it may have momentum for pace, it 

 must have weight to carry ; and to carry that weight, the 

 wings must deliver their blow with effective vertical, as 

 well as oblique, force. 



