INTRODUCTORY REMARKS. 21 



of the division Bacillaria*. These minute creatures are 

 so inconceivably numerous that they cover many miles 

 of surface with several feet of thickness ; as instanced 

 in the polishing-slate and rotten-stone of Bohemia. In 

 Tuscany whole mountains consist almost entirely of the 

 silicified shells of these creatures ; thus combining with 

 each other in infinite numbers, to counterbalance, as it 

 were, their individual minuteness, and to teach the un- 

 thinking this useful lesson, that Nature, in all her ope- 

 rations, is never employed in vain, and that, what are ap- 

 parently her most insignificant productions, fall not be- 

 neath the notice of the profoundest inquirer after truth. 

 To the Botanist the aid of the microscpoe is indispen- 

 sable. In the investigation of our fossil-flora, what does 

 it not exhibit to us ! How beautiful and delicate is the 

 structure of the envelope of some of the fossil-fruits ; those, 

 for instance, of our London clay, when viewed under this 

 instrument! And how important is it, that, by its assis- 

 tance, we can determine with accuracy the natural orders, 

 genera, and sometimes the very species of the trees and 

 plants of former epochs ! How, beyond all question, is 

 now demonstrated the vegetable origin of our coal ! 

 Preserved within a bituminous lump of coal, which has 

 been deposited for thousands of years deep in the bowels 

 of the earth, you may discern not only the woody fibre, 

 its arrangement, and the disposal and form of the 

 medullary rays, but even the most delicate of the vege- 

 table organs, such as the spiral vessels and the beautiful 



* See Natural History of Animalcules, page b'.K 



