(560.7 303 



551.77 

 (579.5 



II. 



The Preparation and Mounting of Chalk Fossils, 



WHILE, doubtless, every collector looks upon one particular 

 formation as the one of supreme interest, it will readily be 

 conceded that the English Chalk occupies a warm corner in the heart 

 of most palaeontologists. Nor is the reason far to seek ; for the fauna 

 of the Chalk is so rich and so varied, the beauty of the fossils so great, 

 the state of preservation so perfect, and the matrix lends itself so 

 readily to skilful manipulation. Indeed, if one excepts certain in- 

 tractable beds, such as the Melbourn Rock and the Chalk Rock, it is 

 the collector's own fault if he fail to obtain an artistic result, and that 

 with no better implements than a knife and a tooth-brush. But, 

 unfortunately, slovenly specimens are the rule, and skilful manipu- 

 lation the exception, and most private collections consist of partially 

 cleaned specimens in shabby cardboard boxes, with loose labels, some 

 of which may providentially be in the right tray. Even in the 

 Government Museums one sees such imperfect work in developing and 

 preserving fossils that one need make no excuse for touching upon 

 apparently elementary points. 



In the first place, with the exception of certain beds to be noted 

 below, all Chalk fossils that come from sea-shore sections must be 

 soaked in fresh water for periods varying with the size of the 

 specimen. Having roughly trimmed the blocks, it will be found 

 sufficient, as a general rule, to soak them for fourteen days, changing 

 the water every day. If this be not done, the salt effloresces on the 

 surface of the specimen as soon as the block dries, and not only 

 disfigures the fossil but often destroys it. The softer the chalk is, the 

 more necessary is it to remove all the salt. And in this, as in all other 

 simple processes, attention to trivial detail is necessary, in order that 

 a satisfactory result may be obtained. Chalk is very porous, and 

 holds a large amount of water. For instance, a pound of dry Margate 

 chalk will take up four ounces of water by weight, and this fact 

 carries with it the conclusion that it is best to immerse the blocks 

 while they still retain some of the moisture of the cHff. The reason for 

 this is made obvious if one drops a piece of dry chalk into water : the 

 imprisoned air is displaced by the water, and seeks the surface with a 

 hissing noise from the Hberation of the air bubbles. Should there be 

 any crack in the chalk the sudden expulsion of the air will cause the 



