244 REPORTS ON THE STATE OF SCIENCE.—1914. 
its effects as a modification of the external factors of the illumination, 
so that the differences observed in the normal eye, under the experi- 
mental condition described above, might in the case of the miner come 
into operation under the condition of his work owing to the altered 
sensational values following retinal insensitiveness. The fact is that 
the theory of ‘ fixational reflexes’ might yet be true of the behaviour 
of the miner’s eye in the coal-mine. 
The conclusion of the research so far then seemed more and more 
to lay stress on the one well-recognised agency, that of illumination, and 
that insensitiveness of the retina really amounted to the same thing 
as an absolute decrease in the illuminant. 
There remains for examination the actual excursion of the eye, and 
an examination into the nervous system of the afflicted miner. 
Since this was written an examination of unaffected miners has been 
made, with the result that there is no appreciable difference between 
their dark-adaptability and what we describe as the normal. 
The Apparatus for estimating the Minimum Light Sensibility in the Process of 
Dark-adaptation. 
It consists of an oblong box, the front of which is pierced by a round hole 
witha diameter of 20 mm., which is covered by an opal disc. At the back of the 
box exactly facing this aperture is a sheet of white paper which reflects light 
thrown upon it on to the disc. At the side of the box is another aperture into 
which a tube nearly 2 m. long fits. This tube carries within it a small 2-volt 
lamp which can be moved quite freely from end to end. The light from this 
lamp is thrown on a mirror so placed that it reflects this light on to the sheet of 
paper, which then reflects it on to the disc. It was only in this way the light 
could be sufficiently diminished to obtain marginal stimuli. 
After a number of experiments we arbitrarily decided upon our zero—that is, 
the light that could be only just perceived five seconds after the room was 
plunged in darkness. At intervals of two and a half minutes the subject was 
tested again, and the lamp was gradually moved away from the box until the 
subject failed to perceive the disc. 
. 
The Investigation of the Jurassic Flora of Yorkshire.—Report 
of the Committee, consisting of Professor A. C. SEWARD 
(Chairman), Mr. H. HamsHaw Tuomas (Secretary), Mr. 
HaARoLD WAGER, and Professor F. EK. WEIssS. 
Tus year attention has been concentrated on the plant beds on and 
near Roseberry Topping, North East Yorkshire, more especially on the 
Thinnfeldia beds. A careful search was made for the reproductive 
structures of Thinnfeldia, and this was rewarded by the discovery of 
numerous associated seed-like bodies, whose structure has yet to be 
investigated, and which may, perhaps, prove to belong to this 
plant. A new example of a Williamsoniella flower-bud was found, 
which is of interest in greatly extending the range of this form. Some 
fruits and seeds, probably referable to the provisional genus Caytonia, 
were also discovered, though they were previously known only from 
Gristhorpe. One or two new forms were found, and many duplicates 
of the more interesting species were collected. It is not proposed to 
continue field-work and collecting in the future on the same scale as 
