116 
The American Geologist. 
February, 18'6 
Decanting must be done with caution and through a fine wire or mus¬ 
lin net as some fronds will be found floating on the solution. The- 
mud is to be similarly handled, taken up with a spatula and placed 
upon a fine netting, and then horizontally lowered into a vessel of water. 
The mud will fall through and all fossils smaller than the mesh remain 
behind. The handling of this “ pay dirt ” with spoon and metallic- 
net would be rather too rough for some delicate fossils. For example,, 
a minute Productus with its hair-like spines would hardly come through 
intact and larval bodies smaller than the mesh would be lost. The 
writer may suggest that a more gentle and surer process is to elevate a 
small portion of the dirt upon a softened blotting paper, transfer it to 
clear water in a shallow porcelain or japanned developing tray, where 
each fossil, however delicate, may be picked up on the end of a camel’s- 
hair brush with a pointed bit of blotting paper for a pusher. 
Wiman finds that highly aluminous clay slates are the most difficult 
matrix to manipulate. With the use of hydrofluoric acid a crust of some 
fluosilicate is formed about the fossil. “Hence I have treated this kind 
of rock first with acetic acid and then with hydrofluoric acid. When 
subjected to acetic acid whatever lime is present is dissolved without 
the fragment losing its form. This process may last for even very 
small fragments for several weeks and must be allowed to continue 
until one is convinced that the lime is all out and the rock throughout 
of a loose consistence. Afterwards the material should be washed for 
several days in water until all lime-salts are removed, and then treated 
with hydrofluoric acid which will soon set the graptolite free.’ - We 
have secured similar results with clay slates having a considerable 
content of lime by the use of pure caustic potash after treatment with 
acid, washing and thorough drying. The real difficulty, however, is to 
isolate fossils of any kind from a clay slate in which the lime content 
is so little that its loss produces no palpable difference in the consis¬ 
tence of the rock. This is the nature of most of the graptolite-bearing 
rocks of America and the winning of the fossils from them is yet to be 
accomplished. 
In treating chert masses the author has set free the graptolites by 
the use of hydrofluoric acid,“acidum hydrofluoricum concentratissimum 
fumans 55 per cent.,” more or less diluted with water. The solution 
is made in a shell of platinum or lead. The process must be interrup¬ 
ted now and then as crystals of some fluosilicate will be deposited on 
some of the exposed parts of the graptolites and load them until they 
break. The rock must then be transferred to another vessel and treat¬ 
ed for a few days with muriatic acid which will dissolve the salt. Then 
the piece may again be treated with the fluoric acid. To reduce in this 
way a piece of chert a half the size of one’s fist takes from one to three 
weeks.” To decolor the graptolite skeletons for microscopic study the 
author has used Schultze’s medium (strong nitric acid with crystals of 
calcium chlorate), but finds it too harsh. With better results he has 
employed eau de Javelle (calcium hypochlorite) and after washing, treat¬ 
ing with alcohol, clearing with turpentine, chloroform or toluol and 
mounting in Canada balsam: 
