380 Correspondence — Mr. TV. T. Aveline — Prof Nicholson. 
have always found it rat, her difficult to prove to a Student that the 
Lower and Upper Carboniferous beds really belong to one formation 
at all, so great is tbe contrast between the “ essentially ” marine 
aspect of tbe lower, and tbe essentially lacustrine aspect of the 
upper division. If tbis be so, is it not “ philosophical ” to suppose 
that tbere is a middle group, between tbese extremes, “ essentially ” 
marine, yet less oceanic tban tbe lower stage of tbe Mountain 
Limestone ? 
Meanwbile, allow me to ask my colleague to defer bis opinion on 
the views I bave stated in my paper tili be bas bad an opportunity 
of reading it. Edward Hüll. 
Geological Suiivey of Ireland, 
Office, 14, Jlume-street, Dublin. 
THE RELATION OE THE PERMIAN TO THE TRIAS. 
Sir, — Mr. Irving appears to bave quite mistaken tbe purport of 
my communication on the relation of the Permian to tbe Trias in tbe 
neighbourhood of Nottingham . 1 I understood it bad been stated by 
geologists of Nottingham, that not only a perfect conformity -existed 
between tbe Permian and tbe New Red Sandstone near that town, 
but tbere was a passage upwards from one formation into tbe other. 
I merely wrote h> say tbis could not be, for tbe reasons I gave. 
But I never intended to imply tbere was not a general conformity 
between tbe two formations, for tbis general conformity must be 
apparent to any one on looking at a good geological map, wbereon 
tbese formations are laid down. Neither did I intend it to be under- 
stood that I considered that tbe break between tbe Permian and the 
New Red Sandstone was greater tban between some of tbe sub- 
divisions of tbese formations. As, for instance, the break between 
the Middle Marls and Lower Magnesian Limestone of the Permian, 
or that between tbe Keuper and the Bunter of tbe Trias. I gave no 
opinion one way or the other on these points. 
The point of my communication was tbis. Tbe relation of tbe 
Permian to tbe Trias I considered an important problem yet to be 
worked out. If a perfect passage from the one up into tbe other 
was found, it would go far to settle tbe question. As far as I know, 
that passage bas not been found, and, I contend, it does not exist in 
tbe neighbourhood of Nottingham. 
Some personal remarks in Mr. Irving’s communication I sliall not 
reply to, they bave nothing to do with the question, and were wbolly 
uncalled for. I do not consider tbe pages of a scientific magazine 
tbe place for that kind of bantering. W. Talbot Aveline. 
HURONIAN. VOLCANIC ROCKS. 
Sir, — In an able paper in your last issue, Mr. George M. Dawson 
publishes the results of bis study of tbe “ Porphyrite Formation ” 
of British Columbia, and applies tbese results to tbe explanation of 
tbe origin of tbe Huronian series of Eastern North America. I am 
particularly pleased to find so good an observer as Mr. Dawson not 
1 Geol. Mag. Dec. II. Vol. IY. p. 155; 
