(EMNGEX. 119 



lu tlie Lower Quurry, immediately upon the yellow marl, 

 there is an extremely fine-grained limestone, which is only J inch 

 in thickness, and splits into yellowish or grey layers as thin as 

 paper. In these layers the plants and insects are imbedded, and 

 often are so wonderfully well preserved that they look as if 

 they had been painted. The insect-bed consists of about 250 

 lamellae, or layers, the formation of which probably occupied a 

 long series of years, during which plants and animals were de- 

 posited at all seasons of the year in this book of Nature. The 

 layers that contain the flowers of the camphor-trees and poplars 

 were probably produced in the spring, those which furnish 

 winged ants and the fruits of elms, poplars, and willows in the 

 summer, and those containing the fruits of the camphor-trees, 

 the Diospyros, the Clematis, and the Synanthereae in the au- 

 tumn. The deposits must have been formed in quiet water and 

 at a distance from the mouth of any river. Probably poisonous 

 gases or vapours rose from this spot into the air and killed the 

 insects flying over the water. The prodigious number of species 

 of insects here met with shows us that not only the animals of 

 the neighbouring shores, but those of a large area, must in the 

 lapse of time have here found their graves. 



Above the insect-bed, in the lower quarry, are several strata 

 of a sandy calcareous marl and white, bluish, and reddish-grey 

 limestones, here and there containing round pebbles, which show 

 that they were produced under the influence of water flowing 

 into the lake. But during the whole period of their formation 

 no aquatic vegetation settled in this spot, perhaps because the 

 gases emitted were unfavourable to the development of plants; 

 and only the leafy trees and cypresses (Glyptostrobas] of the 

 neighbouring forest furnished a certain number of remains of 

 plants, to which were added small vegetable fragments carried 

 by the wind from greater distances. 



In the Upper Quarry the compact indigo-blue marl which 

 covered the bottom of the lake is overlaid by a hard bituminous 

 limestone, which has received the name of Jtettlestone. It is 

 the chief source of the fossil plants of (Eningen. The leaves, 

 the organic matter of which is preserved, are generally of a 

 brown or brownish-yellow colour, and stand out in beautiful 

 relief on the white stone. True aquatic plants are very rare, 



