APRIL 2, 1914] 
NATURE 
115 
married wife keep their heads above water. As 
a means of livelihood he worked for six hours 
every day on the subject catalogue at the Bod- 
leian Library, and only after this work was over 
was he free to study Chemistry for his Oxford 
degree course. In spite of this double call on 
his time, he found opportunity to carry out re- 
search, and in 1886 he began his work on the 
capillary electrometer with the late Sir John (then 
Dr.) Burdon Sanderson, the Professor of Physio- 
logy. From 1887 onwards they did a good deal 
of electro-physiological work together, the 
mechanical details of the apparatus used being 
gradually improved by Burch until the final-present 
day form was evolved. 
Burch also worked out a method for analysing 
the electrometer curves, and in December, 1887, 
wished to publish an account of his discoveries. 
Burdon Sanderson, who was always cautious 
about committing himself, dissuaded him from 
doing so: hence a description of the method was 
not actually published until 1r890, when Einthoven 
independently described his method, and so de- 
prived Burch of some of the credit of the dis- 
covery. In 1892 Burch published a more elaborate 
paper on the time relations of the excursions of 
the capillary electrometer in the Philosophical 
Transactions of the Royal Society, and other 
papers were published later in the Proceedings 
of the society. 
Meanwhile, Burch in 1891 took up lecturing 
under the Oxford University Extension Delegacy, 
and in 1892 he became lecturer, afterwards pro- 
fessor, of Physics at University College, Reading. 
He still lived in Oxford, and went backwards and 
forwards to his work daily. This was a great 
strain on his health, so that in 1909 he broke 
down and had to resign his position, though he 
continued to teach in Oxford. 
In the last eighteen years of his life Burch 
devoted most of his spare time to research in 
colour vision. Among his observations regard- 
ing the physiology of vision were a number 
bearing on the vexed problem of colour sensa- 
tions. He was a convinced adherent of the 
Young theory of colour sense. He _ subjected 
himself to a series of severe experiments in which 
the eye was fatigued to certain colours by pro- 
longed intense stimulation by appropriate parts 
of the prismatic spectrum, and the alteration in 
the colour of other parts of the spectrum when 
observed by the fatigued eye was examined. He 
supplied an interesting memorandum on this 
subject to the’ Board of Trade Committee on 
Sight Tests three years ago. A small book pre- 
senting a practical course of instruction in visual 
physiology embodied the class-work he conducted 
in the subject at the Physiological Laboratory 
at Oxford. It is not only extremely lucid, as was 
everything he wrote, but is stri:kingly original in 
scope and treatment, and contains a number of 
exercises, as, for instance, one on the measure- 
ment of visual acuity, devised entirely by the 
author. His combination of first-hand knowledge 
of physical and physiological experimentation 
NOIZ376, VOLS 93 | 
fitted him to a degree which is quite exceptional 
for success in this branch of scientific study. 
Dr. Burch was elected a Fellow of the Royal 
Society in 1goo. ee DING 
PROG wGs MOM IN CAIN, FiRAS: 
HE death of Prof. George M. Minchin, F.R.S., 
oa March 16, at sixty-eight years of age, 
has deprived science of an earnest and versatile 
investigator, and a wide circle of friends of a 
companion who will be greatly missed. Always 
active in body and alert in mind, Prof. Minchin 
caught the fire of life with both hands, and con- 
veyed its benefits to all around him. 
Prof. Minchin was appointed to the chair of 
mathematics in the Royal Indian Engineering Col- 
lege, Coopers. Hill, in 1875, when he was in his 
twenty-ninth year; and he remained at the College 
until it closed, when he removed to Oxford, where 
he died. He took a leading part in the movement 
for the improvement of geometrical teaching in 
schools; and his little book ‘‘Geometry for Be- 
ginners’’ published in 1898, was an_early and 
very favourable specimen of the methods of the 
reforming party. He was also the author of 
works on “ Statics,” “‘ Uniplanar Kinematics,” and 
‘“Hydrostatics ”; and his treatment of all these 
subjects was original and distinctive. Less well 
known in scientific circles, perhaps, except among 
his friends, is a little volume of verse and prose 
entitled ‘Nature Veritas’ published in 1887. 
His skill in writing verse was of no mean quality ; 
anda humorous example of it will be found in 
Nature of April 14, 1898, in a poem entitled 
“Balnibarbian Glumtrap Rhyme.” He was a 
lover of good English; ‘and this regard for the 
purity of the language made his many contribu- 
tions to our columns clear in expression as well 
as authoritative in opinion. 
Probably the work by which Prof. Minchin will 
best be remembered is that on photo-electricity 
and selenium cells. He began his experiments on 
these subjects in 1877, and was led by them to the 
discovery of many interesting phenomena. He 
observed that electric currents are produced by the 
action of light on silver plates coated with col- 
lodion or gelatin emulsions of bromide, chloride, 
iodide or other silver salts, or with eosin, fluor- 
escein, or other aniline dyes, when the plates were 
immersed in a suitable liquid and one plate was 
illuminated while the other was screened. In 
1891 he exhibited these cells to the Physical 
Society, and also cells made by spreading melted 
selenium on metal plates and immersing them in 
liquids together with an uncoated plate. He 
found that some cells, termed by him ‘‘impulsion 
cells,” had their sensitiveness altered by slight 
impulses or taps, and also by electro-magnetic 
impulses, such as are given by electric sparks or 
a Hertz oscillator at a distance; so that the cells 
embodied the principle of the coherer used for 
the reception of Hertzian waves. 
The form of photo-electric cell afterwards 
