14 ROYAL SOCIETY OF CANADA 
Devonian, or later time. The sedimentary rocks selected were, Trenton 
Limestone of the Ordovician system; and the Boulder clay, Leda clay, 
and Saxicava sands of the Quaternary or Post-tertiary period. Thus 
the specimens examined cover a wide extent in point of geological time. 
The rocks were treated in the following manner. Fifteen 
or twenty grams of the rocks were ground so as to pass through 
an eighty-mesh sieve. One hundred to one hundred and fifty grams 
of fusion mixture (Na*CO* and K?C0*) were added and the whole 
fused in a platinum dish for several hours in a muffle furnace. ~The 
fusion was detached from the platinum dish, was acidified with HCl, 
and evaporated to dryness; then taken up with dilute HCi, and the 
to pump. 

silica and insoluble matter removed by filtration. This insoluble 
matter was treated with hydrofluoric acid, and evaporated to dryness ; 
the small amount of residue was fused as before, and added to 
the soluble portion. The whole was evaporated until a reasonable 
amount of liquid was left, and what remained was stored in a tightly 
stoppered flask for subsequent examination. 
After a definite period, usually about a week, the solution was 
thoroughly boiled, and the expelled air and emanation were collected 
over water. These were drawn into an electroscope which previously 
had been almost exhausted of air by a water pump. Three hours 
later, when the active deposits had nearly reached maximum activity, 
