117 



To obtain the best results with the fossils of the Stfopha. 

 losia and Nautilus beds and similar iiu])nre argillaceous lime- 

 stones, the following ])i-()cess, devised by J. 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 ])erfectly clear. 

 The argillaceous or other im])nrity of the matrix left after 

 the reaction will be exceedingly soft, but I'etain the impres- 

 sions, wdiether 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 ])Ui-e 

 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 liesuthciently 

 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 pi-eserve the hardened matrix, such squeezes must be 

 taken rapidly, lest the heat of the gutta-i)ercha soften the 

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

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

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

 at leisure." * 



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



