NATURAL HISTORY OF THE DIATOMACE^. 419 



petrology, and biology; and it is to be hoped that the results will be, 

 therefore, proportionally valuable and interesting to science at large, and 

 conducive to the welfare more particularly of the citizens of that state. 

 It has been considered desirable, and, in fact, necessary to the proper 

 understanding of the subject, that that portion of the work of the survey 

 which comes within the province of the microscopist should be treated of 

 under more than one head. Thus, at the present time, that part of his 

 investigations which has a particular bearing upon paleontology, or the 

 study of the remains of organized beings found stored up in the form 

 of what are known as fossils in the various strata of the earth, will be 

 treated of, while micro-petrology, or the examination of the minute struc- 

 ture of rock-masses by means of the microscope, will be considered at 

 another time and by another hand, as the bearings of the two branches 

 are so very different. The minor applications of the microscope to the 

 subjects coming under the consideration of the survey will be gone into 

 as opportunity offers and desirability requires. As it is to the study of 

 the remains of the minute forms of extinct beings that micro-paleon- 

 tology is at the present time particularly devoted, the structure of more 

 highly organized beings not having been investigated in this connection 

 to any very great extent, those smaller organisms, their life, history, 

 habits, and relations to geology and the useful arts, will be herein con- 

 sidered ; and we shall begin with a group of organisms whose remains 

 constitute, in some parts of the world, strata of many feet in thickness, 

 underlying cities, and, at other points, make up the greater part of vast 

 mountain chains, and which have in former times played a very impor- 

 tant part in the history of our globe. These are the Diatomacese. 



PART FIRST. 



A Sketch of the Natural History of the Diatomacea. 



As a large majority of the persons into whose hands the present vol- 

 ume will come are ignorant of the characteristics of the group of organ- 

 isms which it is intended to consider, that is to say, the Diatomacese, 

 and as they occupy an important position in the scheme of the geologist, 

 before going into their bearings on paleontology it has been thought 



