No. 3. — A Letter concerning Deep-Sea Dredgings, addressed 

 to Professor Benjamin Peirce, Superintendent United States 

 Coast Survey, by Louis Agassiz. 



Cambridge, Mass., December 2, 1871. 

 My dear Friend, — 



On the point of starting for the Deep- Sea Dredging expedition, for 

 which you have so fully provided, and which I trust may prove to be 

 one of the best rewards for your devotion to the interests of the Coast 

 Survey, I am desirous to leave in your hands a document which may 

 be very compromising for me, but which I nevertheless am determined 

 to write in the hope of showing within what limits Natural History has 

 advanced toward that point of maturity when science may anticipate 

 the discovery of facts. 



If there is, as I believe to be the case, a plan according to which the 

 affinities among animals and the order of their succession in time were 

 determined from the beginning, and if that plan is reflected in the mode 

 of growth, and in the geographical distribution of all living beings ; or, 

 in other words, if this world of ours is the work of intelligence, and not 

 merely the product of force and matter, the human mind, as a part of 

 the whole, should so chime with it, that, from what is known, it may 

 reach the unknown ; and if this be so, the amount of information thus 

 far gathered should, within the limits of errors which the imperfection 

 of our knowledge renders unavoidable, be sufficient to foretell what we 

 are likely to find in the deepest abysses of the sea, from which thus far 

 nothing has been secured. 



I will not undertake to lay down the line of argument upon which I 

 base my statement, beyond what is suggested in the few words pre- 

 ceding, namely, that there is a correlation between the gradation of 

 animals in the complication of their structure, their order of succession 

 in geological times, their mode of development from the egg, and their 

 geographical distribution upon the surface of the globe. If that be so, 

 and if the animal world designed from the beginning has been the 

 motive for the physical changes which our globe has undergone, and if, 

 as I also believe to be the case, these changes have not been the cause 

 of the diversity now observed among organized beings, then we may 



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