AucusT 19, 1915] 
NATURE 
677 

his theory necessary to bring it into line with 
the discovery by Prof. Kamerlingh Onnes that at 
very low temperatures—4° or 5° absolute—the 
electrical conductivities of metals become infinite. 
The external electric field applied to the metal is 
assisted in bringing the axes of the doublets into 
line by the field produced by those doublets already 
in line. The kinetic energy of thermal motion of 
the doublets tends to destroy the alignment. At 
ordinary temperatures it is sufficient to destroy the 
alignment so soon as the external field is with- 
drawn, and the flow of electrons from doublet to 
doublet is stopped. But at very low temperatures 
the energy is not sufficient to modify an alignment 
once produced, and the flow of electrons con- 
tinues when the external field is withdrawn. The 
conductivity in these circumstances will be very 
high. 
From this short account of the present position 
of the two theories it will be seen that the doublet 
theory of Sir J. J. Thomson has shown a greater 
power than the electron theory of co-ordinating 
the facts of experiment. It has difficulties of its 
own, both in the nature of its fundamental 
assumptions and in its power of reproducing the 
facts quantitatively. It does not appear to pro- 
vide electrons for emission by _ incandescent 
bodies, and in its latest development it involves 
serious changes not previously suspected in the 
thermal, thermomagnetic, and thermogalvanic 
properties of metals at the very low temperatures 
attained by Prof. Kamerlingh Onnes. But the 
great flexibility it has shown justifies a more 
generous treatment of it by those authors and 
lecturers who have been content to limit their ex- 
position of these questions to the older electron 
theory. 2H. LEES: 
THE STERILISATION OF 
eS safeguarding of our water supplies is of 
particular importance at the present time, 
for there may be considerable risk of pollution 
if typhoid and cholera cases or ‘‘carriers”’ arrive 
in any number from the seats of war, as may 
well be the case. The research work carried out 
by Dr. Houston is therefore of much value and 
is summarised in a Report just issued.! 
Dr. Houston first deals with his “excess lime ” 
method of purification. The hardness of water is 
chiefly due to bicarbonate of lime (temporary) and 
sulphate of lime (permanent), the former being 
kept in solution by the carbonic acid present. In 
the softening of water lime is added and combines 
with the free and semi-combined carbonic acid, 
causing a precipitation of the lime added and of 
the bicarbonate of lime in the water in the form 
of the relatively insoluble carbonate of lime. A 
water treated with the right amount of lime has 
no caustic alkalinity and has practically no action 
on the bacteria present. When more than enough 
lime is added the water is rendered caustically 

WATER. 
1 Metropolitan Water Board. Eleventh Report on Research Work, 
together with Index to Research Reports, Nos. 1-x inclusive. By Dr, A. C. 
Houston. Pp. vii+s2. (London: Metropolitan Water Board, n.d.) 
Price 2s. €d. 
NO. 2390, VOL. 95] 



alkaline and becomes actively bactericidal. Such 
a water would, however, be unfit for domestic and 
trade use, but if the excess of lime present be 
removed by the addition of a sufficiency of water 
from which the bacteria have been removed, the 
whole of the mixed water will be softened and 
purified, and will be satisfactory for all purposes. 
Dr. Houston has previously shown that if raw 
river water be stored for from four to five weeks 
the great majority of the bacteria are removed, and 
the water is rendered safe for drinking purposes. 
The excess lime method of purification consists, 
then, in the addition of an excess of lime, storage 
of the alkaline water for a day or thereabouts, 
so that the bactericidal action may be exerted, 
addition of a sufficiency of water, purified by 
storage, to neutralise the excessive alkalinity, and 
filtration to remove the precipitated carbonate of 
lime., 
Dr. Houston has tested the method on a large 
scale at Sunbury and at Aberdeen. At Aberdeen 
Bacillus coli (which may be taken as an index of 
pollution) was present in the untreated water in 
from I c.c. to 100 c.c.; after treatment it was not 
found in 100 c.c.; the process is therefore efficient 
and it is comparatively inexpensive. 
Another research which has been carried out by 
Dr. Houston is an investigation of “water 
microbes” giving the cholera-red reaction after 
incubation of cultures for twenty-four hours. The 
cholera-red reaction (obtained by adding acid to 
a culture) is a very constant and characteristic 
reaction of the cholera microbe, and as this 
organism is frequently conveyed by water, it is 
important to know whether water organisms other 
than cholera yield the reaction. It is satisfactory 
to find that, although eighty microbes out of 
approximately 1885 sub-cultures gave the cholera- 
red reaction on first being tested, they were easily 
distinguished from cholera by the application of 
two or three further simple tests. 
Dr. Houston is to be congratulated on the 
valuable research work he has been able to carry 
out in the midst of a vast amount of routine work. 
R. T. HEWLETT. 
THE LATE PROF. J]. COOK WILSON. 
EATH has of late been busy among Oxford 
residents. The demise of John Cook 
Wilson, Wykeham Professor of Logic, was not 
unexpected, for he had been in bad health for 
more than a year, and indeed had never recovered 
completely from the shock of his wife’s death in 
January, 1914. Cook Wilson was a man of quite 
exceptional attainments. Born at Nottingham 
and educated at Derby School, he matriculated at 
Oxford in 1868. As scholar of Balliol he took no 
fewer than four first classes, two being for mathe- 
matics and two for classics. These were followed 
by the Latin Essay, the Conington Prize, and a 
fellowship at Oriel. After his election as Wyke- 
ham Professor he became a fellow of New Col- 
lege, but his affection for Oriel never waned, and 
his connection with his old college was of late 
