464 Notices of Memoirs—British Association. 
cordierite, a decrease in the latter is to be accompanied with an 
increase in the former. Inthe present case the percentage of magnesia 
is also low. ‘The ferrous equivalent of the sum of ferrous oxide and 
magnesia does not fall below 22 per cent in the analyses given by 
Dana, while it is as high as 27 per cent in the case of Finland 
cordierite. The percentage of alumina usually does not go beyond 
83, whereas in the present case it is as high as 35:2. The other 
constituents remain within normal limits. If we may rely on the 
accuracy of this analysis, this cordierite is of a peculiar constitution. 
It must, however, be remembered that there is just a possibility of 
error in the determination of the two oxides of iron. 
The positive character of some of these cordierite crystals is 
confirmed by the observations of Mr. G. dep. Cotter, Assistant Super- 
intendent, Geological Survey of India. His remarks on the mineral 
are given below :— 
‘‘In the slide which Mr. Chacko now sends I find that one section 
of cordierite gives a positive figure and one section gives a negative 
figure. I have also found a positive figure from the cordierite from 
Vizagapatam, 16/189. his is probably due to the increase of the — 
value of 2V beyond 90° (see Iddings). 2V in cordierite is very 
variable, and the lower the refractive the greater is 2V. The 
mineral sent now by Mr. Chacko has been tested by the method of 
Schroeder Van der Kohlk, and its refractive index lies between nitro- 
benzene and cedar oil, and it gives reds and blues for a mixture of 
both. Therefore its refractive index is about 1:53, that is, fairly 
low. We may then conclude that 2V is probably large. In fact, 
T agree with what Mr. Chacko suggests, and think it might be worth 
publishing if he cares to do so. There is no section in the slide 
suited to the actual measurement of 2V.” 
NOTICHS OF MEMOIRS. 
I.—BritisH AssocraTION FOR THE ADVANCEMENT OF Science, Erenty- 
sixtH AnnuAL Mertine, NewcastLe-upon-Tynb, SePrEMBER 6-8, 
1916. 
List or AuTHoRS AND TITLES oF PAPERS READ IN SECTION C (Gxotoax). 
Presidential Address by Professor W. S. Boulton. 
Professor G. A. Lebour.—Address on the Local Geology. 
Dr. D. Woolacott.—Some Notes on the Permian of Durham. 
Dr. @. Hickling. —Underground Contours of the Black Mine. 
Professor W. G. Fearnsides. —Underground Contours of the Barnsley 
Mine. 
Joint Meeting with Section E in the Room of Section OC. 
Dr. A. Wilmore.—The Physical Geography and Geology of the 
Northern Pennines. 
Professor W. G. Fearnsides and Dr. P. G. H. Boswell.—Note on the 
Occurrence of Refractory Sands and Associated Materials occurring 
in Hollows in the Surface of the Mountain Limestone District of 
Derbyshire and Staffordshire. 
Dr. P. G. H. Boswell.—Geological Characters of Sands used in Re. 
Manufacture. 
