XCIV ROYAL SOCIETY OF CANADA 



"The abrupt way m wliieh the beds end on and against the granite 

 seems to me to ])reclude any other supposition than that the granite 

 represents what was once the downward extension of the Silurian 

 strata. 



" I know of no instance here wliere the granite has clearly upheaved 

 and thrown off the stratified rocks. Large areas of granite appear at the 

 surface in all parts of the colony, but the ordinary dip and strike of the 

 sti'atitied rocks is in no case either detiected or otherwise influenced. 

 Along tlie margins, however, the granite and the stratified rocks are 

 more or less interlaced, and the evidence of metamorphism gradually 

 dimniishes as you recede from the granite. The ex])osui'e of the granite 

 is clearly due to the removal by denudation of the once superincumbent 

 strata.'" 



At that time (1867) 1 was corresponding with Jukes, the director of 

 the Geological Suiwey of Ireland, on the subject of granite ; and in a let- 

 ter from him. 28th July, 1867, two years after the letter above quoted 

 was written. I find the following : •' As to granite, there are two kinds ; 

 one merely an extreme form of gneiss • made in situ.' It is clearly an 

 intrusive mass, and alters the rocks it cuts into, and is sometimes com- 

 pletely altered by them. I believe that the clearly intrusive granites of 

 Leinster and of Devon and Cornwall form an undulating floor which cuts 

 off all the superincumbent rocks which dip down and end abruptly 

 against it. as you say it does in Victoria." Jukes then referred to the 

 granite of the Mourne Mountains, sending mo a rough sketch ilhistrating 

 the facts. This ver}- section is reproduced on page 542 of Geike's " Text- 

 book," 18i>5, and is there referred to as '"this remarkable structure." 

 .Jukes continues : "Nevertheless 1 believe that the granite slowly worked 

 its way upwards as an original molten mass, constantly eating into and 

 absorbing some of the overlying rocks. I quite agree with j^ou that the 

 intrusion did not affect the strike of the rocks or disturb them at all." 



Jukes'si views on this subject are fully given in chapter xvii. of his 

 " Manual," 1862. Ramsay, in his address to Section C of the British 

 Association, 1866, as also in the several editions of his "Physical (feology 

 and Geography of Great Britain," 1864: to 1808, held similar views. In the 

 latter, referring to Sorby, on granite, he writes : " If the above views be 

 correct, though many granites, having been completely fused, have been in- 

 jected amongst strata, and are thus to be classed as intrusive rocks ; yet, in 

 the main, so far from the intrusion of granite having produced many moun- 

 tains by mere upheaval, both gneiss and granite would rather seem to be 

 often the results of the forces that formed certain mountain chains. Pos- 

 sibly the result was connected with the contraction of the earth's crust, 

 and the heat produced by the intense lateral jnv.ssure that, with much 

 movement of parts, produced the contortion of vast masses of strata, 

 parts of which, now exposed by denudation, were then deep under- 



