Notes and Comments. I2T 
were said to be unique, and some dozen types from other 
areas, including Sandown, Portmadoc, Olney, Somerton, Lyme 
Regis, and Merivale Park were examined in detail with reference 
to :—(a) Evidence furnished by distorted fossils ; (b) Chemical 
composition ; (c) Geometrical similarities; (d) Microscopic 
structures. The Author critically examined the accepted 
hypothesis that cone-in-cone structure is something essentially 
due to crystallization. He concluded from the evidence of 
experiments (i) that cone-in-cone is not due to crystallization, 
but is a mechanically produced structure due to great and 
localized pressure ; (ii) that it is closely allied to the phenomenon 
known as pressure solution ; (iii) that cone-in-cone structure is 
closely associated with other rock-structures which are mutually 
indicative the one of the other, and also of their mode of origin. 
PROFESSOR BONNEY ON CONE-IN-CONE. 
At the meeting a letter was read from Prof. Bonney, viz :— 
“In the Mineralogical Magazine, vol. xi., p. 24, I published a 
paper discussing the origin of cone in cone structure, which 
was in general agreement with, but supplementary to, the work 
of Sorby; Mr. W. S. Gresley, and Prof. G. A. J. Cole. Though 
I had for some years been examining specimens which showed 
this structure, it was not until 1892 that I chanced to come 
across a good instance of it in the field. That occurred in the 
upper part of the Wealden formation at Sandown Bay, in the 
Isle of Wight. The lower portion of the specimen contains, in 
a rather muddy calcareous matrix, numerous more or less 
imperfect valves of lamellibranchs (? Cyrena), a few gastropods 
(probably Paludina), and numerous valves, double or single, of 
ostracods, together with a few subangular fragments of quartz. 
The upper portion is a homogeneous dirty limestone. In it 
the “shaving brush” crystalline structure is well developed. 
It is true that this bed forms part of the Isle of Wight anticline, 
but none of the organisms, and no part of the specimen, show 
the slightest sign of crushing 77 situ, or of any kind of disturb- 
ance from pressure. Evidence of that is tendered in the paper, 
and reasons are given for believing that the spiral cracking of 
the cone in cone is the result of contraction, probably in 
drying. Thus, to whatever inductions the Author’s experi- 
ments and observations may lead, I am obliged to regard them 
as incompatible with all the specimens that I have examined 
and must continue to maintain, as stated in the concluding 
words of my paper, published in 1894, that cone in cone 
structure is primarily due to crystallization, but the develop- 
ment of it—‘‘ its existence in short as cone in cone—is due to 
contraction subsequent to this crystallization, and thus the 
mechanical cause is not less essential than the chemical for its 
formation.” ’ 
1915 April 1. 
