CONSTRUCTION OF THE EAKTH. 159 



ten-stone of Germany, forming beds sometimes fourteen 

 feet thick, is made up mostly of silicious shells so mi- 

 nute that a cubic inch contains forty-one thousand million 

 (41,000,000,000), the weight of a single shell being cal- 

 culated to weigh the yj^j. millionth part of a grain. Si- 

 licious deposits from vegetables and animals are often 

 mingled with calcareous deposits, and hence came for the 

 most part the flint-stones, which, as you will see here- 

 after, are so often found in chalk. One tenth of the oaze 

 ( 239) is silicious. So much agency are the minute 

 silicious animalcules and plants known to have had in 

 furnishing material for silicious rocks, that some have 

 supposed that most rocks of this kind have received their 

 material from this source. 



I remark in passing that, although the diatoms of 

 which some forms are given in Fig. 84 have heretofore 

 always been considered as animalcule, Professor Dana 

 states that they are now regarded as vegetable. 



241. Seas, Lakes, and Rivers. I have thus shown you 

 what means have been employed in the building up of 

 that part of the earth which is included under the gen- 

 eral term land. The great cavities of the sea, "the 

 store-houses" in which God "layeth up the depth," we 

 know less about, and our researches are confined mostly 

 to the comparatively shallow portions of the ocean which 

 skirt the land. The manner in which the rivers that 

 run into the sea are made I need not stop to point out 

 to you. The streamlets made by every shower illus- 

 trate that subject, so that, with what has already been 

 said in regard to rivers, your own observation can give 

 you a proper insight into it. The same can be said, for 

 the most part, of the lakes. 



242. Plan in the Construction of the Earth. Enough 

 has been developed in what I have said of the constguc- 

 tion of the earth to show you that, although there have 

 been commotion and much apparent confusion, there has 

 been a well-ordered plan throughout all the changes, 



