222 



Baron Ettingshausen. 



[Dec. 19, 



mere palaeontological interest, but above all to extend it to the unveil- 

 ing of the history of the development of the whole vegetable kingdom. 



As in studying the Eocene Flora of Great Britain I shall follow the 

 path of the inquiry which I originally took, I must begin by giving an 

 account of my method of investigating fossil plants, and I shall then 

 explain the results which I have obtained. 



I. — The Method of obtaining Fossil Plants. 



It has been usual to collect fossil plants by splitting the pieces of 

 rocks with a hammer. The more a stone has been exposed to the action 

 of the weather, the easier it is to break it and lay bare what is within. 

 But fossil plants found under such circumstances are no longer in good 

 preservation : they have suffered greatly from exposure to the weather, 

 and generally only the outlines are visible ; their structure and the finest 

 veins of the leaf- skeleton are lost. Stone when it has not been exposed 

 to the air is not easily split ; the more compact it is the more difficult 

 it will be found to obtain the fossils in this way. Under favourable 

 circumstances only fragments of the fossils are obtained. By the 

 forcible splitting of pieces of rocks with a hammer it is only possible 

 to succeed very imperfectly in obtaining fossil plants, besides which it 

 must always be a lucky chance that the hammer strikes that part of 

 the stone in which the plants lie concealed, and that it has not been 

 injured by the blow, for a large number of fossils are lost in this way, 

 or remain undiscovered in the stone. I have found a method by which 

 fossil plants can be satisfactorily got out of the most compact rocks 

 without using a hammer. 



The pieces of rocks are for a considerable time subjected to a 

 thorough soaking under the pressure of two or three atmospheres. In 

 an iron vessel full of water brought into connexion with a stand-pipe 

 the stones are left lying for half a year (most advantageously in summer- 

 time). In those places where there is a fossil in the stone the material 

 of the stone is not continuous. Thus numerous, often microscopi- 

 cally small, splits and other hollow spaces are found along the fossil 

 plants. These hollow spaces get filled little by little with water. Then 

 the stones which have been treated in this manner are exposed to an 

 intense cold, —15° to 20° C. The water in the hollow spaces is 

 turned into ice, and by this means the stones are burst asunder on the 

 spot where there are petrifactions. The stones open of themselves, 

 and show what they contain. The more compact the stone the surer 

 and more complete by this method is the successful acquisition of the 

 fossil plants. They show .the original state in which they were pre- 

 served. With very hard stones the soaking and the subsequent 

 freezing must be frequently repeated. On the first action of the frost 

 the splits and hollow spaces are widened by the formation of ice within 

 them to the surface of the stone. These must be quite filled again with 



