INTRODUCTION 5 



which we have to bring: in illustration of the de- 



o 



signs of nature, is, therefore, not perfect, since 

 sometimes the material is different, sometimes the 

 end to be attained is not precisely the same ; and, 

 above all, in the animal body a double object is 

 often secured by the structure or framework, 

 which cannot be accomplished by mere human 

 ingenuity, and of which, therefore, we can offer 

 no illustration strictly correct. 



However ingenious our contrivances may be, 

 they are not only limited, but they present a 

 sameness which becomes tiresome. Nature, on 

 the contrary, gives us the same objects of inter- 

 est, or images of beauty, with such variety, that 

 they lose nothing of their influence and their 

 attraction by repetition. 



If the reader has an imperfect notion of design 

 and providence from a too careless survey of ex- 

 ternal nature, and the consequent languor of his 

 reflections, we hope that the mere novelty of the 

 instances we are about to place before him may 

 carry conviction to his mind ; for we are to draw 

 from nature still, but in a field which has been 

 left strangely neglected, though the nearest to us 

 of all, and of aU the most fruitful. 



Men proceed in a slow course of advancement 

 in architectural, or mechanical, or optical sci- 

 ences ; and when an improvement is made, it is 

 found that there are all along examples of it in 



