1 84 ANCIENT PLANTS 



APPENDIX II 

 TREATMENT OF SPECIMENS 



1. The commonest form in which fossils are collected is that 

 which has been described as impression material (se& p. 12). In 

 many cases these will need no further attention after the block 

 of stone on which they lie has been chipped into shape. 



In chipping a block down to the size required it is best to 

 hold it freely in the left hand, protecting the actual specimen 

 with the palm where possible, and taking the surplus edges 

 away by means of short sharp blows from the hammer, striking 

 so that only small pieces come away with each blow. For 

 delicate specimens it is wise to leave a good margin of the 

 matrix round the specimen, and to do the final clearing with a 

 thin-bladed penknife, taking away small flakes of the stone with 

 delicate taps on the handle of the knife. 



Specimens from fine sandstones, shales, and limestones are 

 usually thoroughly hard and resistant, and are then much better 

 if left without treatment; by varnishing and polishing them 

 many amateur collectors spoil their specimens, for a coat of 

 shiny varnish often conceals the details of the fossil itself 

 Impressions of plants on friable shales, on the other hand, or 

 those which have a tendency to peel off as they dry, will require 

 some treatment. In such cases the best substance to use is a 

 dilute solution of size, in which the^specimen should soak for a 

 short period while the liquid is warm (not hot), after which it 

 should be slightly drained and the size allowed to dry in. The 

 congealed substance then holds the plant film on to the rock 

 surface and prevents the rock from crumbling away, while it is 

 almost invisible and does not spoil the plant with any excessive 

 glaze. 



2. For specimens of casts the same treatment generally ap- 

 plies, though they are more apt to separate completely from the 

 matrix after one or two sharp blows, and thus save one the work 

 of picking out the details of their structure. 



3. Those blocks which contain petrifactions, and can there- 

 fore be made to show microscopic details, will require much 

 more treatment. In some cases mere polishing reveals much of 

 the structure — such, for instance, were the " Staarsteine " of the 

 German lapidaries, where the axis and rootlets of a fossil like a 

 treefern show their very characteristic pattern distinctly. 



As a rule, however, it is better, and for any detailed work it 



