R. A, Daly — Mechanics of Igneous Intimsion, 117 



" In one quarry, also, there was an elevation of a part of the 

 bed forming the floor. It was an anticlinal axis of more than 

 800 feet in length, and its trend was nearly east and w^est. In 

 its most conspicuous part the elevation was from 6 to 8 inches, 

 and the arch measured from 16 to 18 feet from base to base 

 over the crest."* 



Notwithstanding the spectacular nature of these sample 

 phenomena observed in different quarries, the forces engaged 

 in their production are almost insignificant compared with 

 those which must be produced in the shell of country-rock 

 concentric with the molar contact of a still molten stock or 

 batholith. The latter forces may be compared with the force 

 of compression which has so often developed peripheral cleav- 

 age and schistosity concentric with molar contacts of stocks and 

 batholiths ; but fracture is the necessary product of the one 

 kind of energy applied suddenly, as rock-flowage is the product 

 of the other applied slowly and for a much greater period of 

 time. 



Differential heating of the invaded formation will, then, 

 through exfoliation and still more irregular shattering, cause 

 the mechanical destruction of the chamber-vault. If the 

 magma be thoroughly molten, the rock-fragments so immersed 

 in it, will, by the balance of probabilities for the average case, 

 sink in the magma. The new surface of the country-rock so 

 exposed to the hot magma must undergo a similar process. 

 The magma chamber may in this w^ay be gradually enlarged 

 so long as the magma preserves sufficient heat for the purpose. 

 ]^ear the time of final solidification the high viscosity must 

 prevent the sinking of the blocks which are last isolated in the 

 magma. The '' zone of inclusions " and its organic relation to 

 the molar contact actually to be observed in plutonic rock- 

 bodies seem to find adequate explanation by this hypothesis. 



Illustration from the Madoc- Marmora District of Ontario. 



The best published example of a granite stock mapped with 

 the distinct purpose of illustrating a sliatter-zone is doubtless 

 that due to the labors of Coste and White in the Madoc-Mar- 

 mora Mining District of Ontario. f A. reduced copy of the 

 map is represented in fig. 1. The legend expresses practically 

 all the information yet printed in connection with the region 

 since the survey was made. Mr. Coste has kindly given the 

 writer certain additional statements on this interesting group 

 of granite bosses ; the following quotations are taken from his 

 letter dealing with the matter. '^ You are quite right in your 



* Julien, op. cit., p. 391. 



f Geol. and Nat. Hist. Surv. of Canada, Special sheet ; 3^ mile to 1 inch, 

 published without text, 1886. 



