366 
tion, by those who uphold so strenuously that the trap forma- 
tions of the carboniferous period of Scotland are the lavas of 
submarine volcanoes. > 
If it were necessary to give the authority of a living geologist 
for the truthfulness of our ideas regarding these so-called 
igneous rocks, Mr. Geikie might be referred to. He read a 
paper before the Geological Society on the 6th of last June, 
and wrote also an article which appears in the December number 
of the Geological Magazine (1866) ; in both of which he shows 
that sandstones and clay, as well as limestones, can be seen 
passing into trap and granite in Ayrshire ; and that without 
either °rising from their beds or being overheated in them.* 
Speaking of sandstones, he says that they “ have become 
changed in places into a rock of variable composition, 
which is sometimes quartzless syenite, sometimes mmette 
or mica-trap,” and goes on to show how crystalline struc- 
ture is fully reached. “ At last,” he says, “ I am therefore 
forced to conclude that the crystalline rocks, described above, 
have resulted from the alteration, in situ , of certain bedded 
deposits.” It is interesting to see the effect of this conclusion, 
as to sandstone passing into trap and granite, in connection 
with these rocks passing into each other. Sir Charles Lyell 
says, “ It would be easy to multiply examples to prove that 
the granite and trap rocks pass into each other, and are 
merely different forms which the same elements have assumed 
according to the different circumstances in which they have 
consolidated from a state of fusion.” — ( Principles , vol. in. p. 
362, ed. 1833.) Now, sandstone and even clay, passing into 
trap and granite, must be classed among the fused rocks too, 
or the whole “ fused” theory of trap and granite must be 
given up. If the positive statements as to the origin of 
trap rocks, which so abound in our popular geology, taken 
along with what we have thus stated, do not prove ignorance 
of fundamental truth in the science, nothing can be proved. 
"Wlien we would account for geological belief as to the origin 
of certain strata — belief that is so palpably false we have only 
to mark the oblivion which prevails as to some of the grandest 
discoveries of kindred sciences. Our great leading geologists 
* Mr. Geikie says, near tlie commencement of Ms paper in the magazine, 
“ The rocks referred to below are Diorite, JMinette, and Granite , all of which, 
with one exception, are admitted by most geologists to have generally had an 
igneous origin — that is to say, they have not only been in a state of fusion, 
but have also at various periods forced themselves among pre-existing strata. 
The exception is Granite evidently. Mr. Geikie lets the fused theory down 
gently , but he lets it down effectually. 
