117 



To obtain the best results with the fossils of the Stropha 

 losia and Nautilus beds and similar impure argillaceous lime- 

 stones, the following process, devised by .1. M. Clarke, is 



recommended : " Let small fragments exposing fossils in sec- 

 tion be placed in dilute muriatic acid, until the calcareous 

 matter is removed to a sufficient depth from the surface to 

 leave all impressions of fossils at the surface perfectly clear. 

 The argillaceous or other impurity of the matrix left after 

 the reaction will be exceedingly soft, but retain the impres- 

 sions, whether external or internal, with exceeding delicacy 

 of detail. The fragments may then be carefully removed 

 from the acid and washed, by placing for a moment in pure 

 water. They should then be thoroughly dried, and after- 

 wards hardened, by cautiously soaking in a very weak solu- 

 tion of glue, care being taken that this solution besufficiently 

 thin to enter all the ornamental or structural cavities and 

 interstices of the impressions. After again drying, soft, clean, 

 and clear squeezes are to be taken with soft gutta-percha. 

 To preserve the hardened matrix, such squeezes must be 

 taken rapidly, lest the heat of the gutta-percha soften the 

 glue and cause adhesion. If, however, the destruction of the 

 matrix is not of moment, the gutta-percha may be with- 

 drawn at will, and the adhering dirt soaked and washed off 

 at leisure." * 



* 14th Ann. Rep't, N. Y. State Geol., 1894, p. 100. Footnote. 



