present in Rocks in the Neighbourhood of Montreal. 233 



For Professor Rutherford has shown by his calculations that 

 the heat from *05 x 10~ 12 gram of radium in every gram of 

 the earth would be sufficient to compensate for the loss of 

 heat from the earth by conduction and radiation. But the 

 averages obtained from Strutt's determination are : — 



Igneous rocks 1*7 X 10~ 12 gram of radium. 



Sedimentary rocks ... 1*1 x 10 -12 „ „ 



Mean value T4 x 10~ 12 



Hence it appears that near the earth's surface there is 

 about 28 times as much radium present as will account for 

 the existing temperature gradient within the earth. This 

 result is so unexpected that it seems desirable to check all 

 available data before embarking on speculative hypotheses. 

 Moreover Strutt, in his work, ignored the twin continents 

 of North and South America, for he did not select a single 

 specimen for investigation from the New World. 



For these reasons the present writers decided to examine 

 representative rocks obtained in the immediate neighbour- 

 hood of Montreal. Professor F. D. Adams kindly recom- 

 mended a typical series, and his assistant, Mr. Bancroft, 

 was good enough to procure specimens from the field. 



Three igneous rocks were selected : — Essexite, which forms 

 the main mass of Mount Royal ; Nepheline Syenite, a sub- 

 ordinate part of the same mountain, and Tinguaite ; which 

 occurs as a large intrusive sheet. All these were thrust 

 through the Ordovician plain in Devonian or later times. 

 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 chemically prepared in the following 

 manner : —Fifteen to 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 2 C0 3 and 

 K 2 C0 3 ) were added, and, the whole fused in a platinum dish for 

 several hours in a muffle furnace. The fused mass was detached 

 from the platinum dish, acidified with HC1, and evaporated to 

 dryness ; then taken up with dilute HC1 and the silica and 

 insoluble matter removed by filtration. This insoluble matter 

 was treated with hydrofluoric acid, evaporated to dryness, and 

 the small amount of residue was fused as before, and added to 

 the soluble portion. The whole was evaporated until a reason- 

 able amount of liquid was left, and this was stored in a 

 tightly stoppered flask for subsequent examination. 



Phil. May. S. 6. Vol. 14. No. 80. Aug. 1907. R 



