this research is to find a glass that will cut off as 
much as possible of the heat radiation, 1 have also 
attacked the problem from the ultra-violet and the 
transparency points of view. Taking each of these 
desiderata by itself, I have succeeded in preparing 
glasses which cut off more than 90 per cent. of heat 
radiation, which are opaque to the invisible ultra- 
violet rays, and are sufficiently free from colour to be 
capable of use as spectacles. But I have not been 
able to combine in one specimen of glass these three 
desiderata in the highest degree. The ideal glass 
which will transmit all the colours of the spectrum, 
cutting off the invisible rays at each end, is still to 
be discovered. 
So far as transparency, however, is concerned, it 
will not be an unmixed advantage for the sought-for 
glass to be quite clear and colourless. The glare of 
a strong light on white cliffs, expanses of snow, 
electric light, &c., is known to be injurious to the 
eye, and therefore a tinted glass combining good 
ebstruction to the heat radiation and ultra-violet rays 
is the. best to aim for. 
For ordinary use, when no special protection against 
heat radiation is needed, the choice will depend on 
whether the ultra-violet or the luminous rays are 
most to be suppressed, or whether the two together 
are to be toned down. Ordinarily the visible spectrum 
is assumed to end at the Fraunhofer line K, 3933, 
but light can easily be distinguished some distance 
beyond by the naked eye. It may therefore be con- 
sidered that the ultra-violet rays which are to be cut 
off on account of their possible injurious action are 
those of shorter wave-lengths than, say, 3700. Many 
glasses have been prepared for this purpose, all of 
which are opaque to rays shorter than 43700. The 
colours are pale green, yellow, and neutral; they 
transmit ample light so that ,a choice of tints is 
available to suit individual taste. 
Glasses which are restful to the eyes in the glare 
of the sun on chalk cliffs, expanses of snow, or 
reflected from the sea, of yellow, green, and neutral 
tints, have also been prepared which have the advan- 
tage of cutting off practically all the ultra-violet rays 
and also a considerable amount of the heat radiation. 
GEOLOGY AT THE BRITISH 
ASSOCIATION. 
(oP the conclusion of Prof. E. J. Garwood’s presi- 
dential address, which has been published in 
full in a previous issue, Prof. Lapworth gave an 
address on the geology and physical geography of the 
country round Birmingham, which was supplemented 
by a description of the igneous rocks of the district 
by Prof. W. W. Watts. Prof. Lapworth’s address 
dealt with the broad features of the topography and 
stratigraphy of the area, special reference being made 
to some of the places to be visited on the field excur- 
sions. 
Mr. George Barrow described the typical Spirorbis 
Limestone of North Warwickshire as a rather compact 
rock, usually grey, and containing Spirorbis carbon- 
arius. Two main beds occur, the Index Limestone 
about 1oo ft. down in the Halesowen group, and 
another less persistent bed close to the base of the 
Keele group. There are other less continuous bands, 
and also lenticles and scattered nodules. He attri- 
buted the formation of the limestone to the evapora- 
tion of shallow sheets of lime-bearing water, a view 
which is supported by the structure of the rock, during 
a dry epoch, subject to sudden or periodical floods. 
The stream-courses of the Black Country plateau 
feted the subject of a communication by Mr. Henry 
Kay. 
NO. 2299, VOL. 92] 
The area was described as including the anti- 
NATURE 
cline of the South Staffordshire Coalfield plus the 
north-western parts of Cannock Chase and the War- — 
ley-Barr area. The chief physical feature is the mid- 
land watershed which runs across the plateau from — 
Wolverhampton to the Lickeys. The Trent drains — 
the larger part of the area, but the southward mar- — 
ginal drainage flows into the Severn. The Trent 
drainage area has been subjected to excessive piracy 
and has steadily suffered loss. The northern drainage _ 
is consequent on the formation of the South Stafford- 
shire anticline, regarding the age of which it bears — 
notable evidence. The author states that the uplift — 
is, in part at least, post-Tertiary. a 
Prof. Sollas exhibited a number of flints showing 
outlines similar to those described as “rostro- — 
carinate,”’ and supposed to be of human workman- — 
ship. He described the conditions under which they — 
were found, and expressed his firm belief in their — 
formation by the action of surf upon nodules of flint — 
partially embedded in the deposits of the beach, the — 
curved keel being produced by the intersection of two _ 
conchoidal fracture-surfaces. ’ 
In a paper on the structure of the Lias Ironstone ~ 
of South Warwickshire and Oxfordshire Mr. E. A. — 
Walford inferred that the sea-floor of the Middle Lias — 
was a tangle of crinoid growth, stage above stage. 
He described beds of the Middle Lias stone as packed — 
with curved and interlacing stems lying upon the ~ 
bedding plane, with other beds of the fine pentangular — 
and smaller ossicles of crinoids between. eo 
Mr. T. C. Cantrill described the occurrence of — 
Estheria, cf. minuta, in the Bunter pebble bed of 
Ogley Hay, near Walsall. The fossils were found 
in two thin bands of red marl in a disused sand-— 
quarry. 4 
The flora and fauna of the Upper Keuper Sand- 
stones of Warwickshire and Worcestershire formed 
the subject of a communication by Messrs. L. J. 
Wills and W. Campbell Smith. They described for — 
the first time from the English Trias examples of the — 
foliage and scales of the female cone of a Voltzia, 
closely resembling V. heterophylla, of the Bunter of — 
the Vosges, and recorded new occurrences of Voltzia, 
Schizonema, Carpolithus, and, possibly, Yuccites, — 
The fauna includes Phaebodus brodiei, Semionotus, 
and Ceratodus, also the lamellibranch Thracia? — 
brodiei, and the authors conclude “that we are not 
dealing with a pre-Rhztic incursion of the sea, but 
with a littoral facies of the Keuper Marls, formed 
where the water was at times sufficiently fresh to 
support a small fish-fauna and in sufficient motion to — 
move coarse sediments.”’ . a 
Nodules from the Basal Ordovician conglomerate at 
Bryn Glas, Ffestiniog, were exhibited by Prof. W. G. — 
Fearnsides, and some discussion as to their nature 
and origin took place. P 
Dr. A. Vaughan made a communication on the 
division between the Lower and Upper Avonian with — 
a view to the discussion of several important questions 
of nomenclature. Sa 
Mr. F. G. Meachem contributed a paper on the ~ 
progress of the coal-mining industry of the South — 
Midlands since the year 1836, from which the follow- — 
ing figures are quoted :— 
Areas of the Known Coalfields of the Area in Square — 
Miles, 
1836 1913 
South Staffs 70 360 
Leicester ee 20 88 
Warwick mie are) 222 
Salop .... Ae 20 096 
Total S20 -66 
