NATURE 
[May 2, ro12 
Prof. Cohen claims that his figures for soot forma- 
tion agree substantially with those obtained by the 
late Sir W. Roberts-Austen; but do they? Sir W. 
Roberts-Austen’s figure was 6 per cent. of soot on 
the coal burned, whilst Prof. Cohen’s figure is 6:5 
per cent. of soot on the carbon burnt to carbon 
dioxide—carbon dioxide being the product of com- 
plete combustion, whilst soot has been defined by the 
authors as a product of incomplete combustion. 
As pointed out in the review, no such method as 
that employed by the authors can give even approxi- | 
mately accurate results unless the carbon escaping as 
carbon monoxide and hydrocarbons is also estimated ; 
and when Prof. Cohen says that the reviewer fails 
to see that the percentage of soot on carbon burnt 
can be easily calculated on the fuel used if the 
amounts of carbon in the fuel and carbon dioxide in 
the flue gases are known, he is truly stating the case. 
In conclusion, I can only say that my opinion of 
the book is unchanged by Prof. Cohen’s reply, and 
that it is a pity that so excellent a work has been 
marred by the points to which attention was directed 
in the review 
THe REVIEWER. 
Remains of Prehistoric Horse in the Stort Basin. 
WirHIN the last few weeks a metatarsal and an 
astragalus identical in type with those previously 
found at Bishop’s Stortford (see Report B.A., Ports- 
mouth meeting, Ig1I, p. 521) have been exhumed 
from beneath 3 ft. of native peat and 2 ft. of an 
overlying pond-silt of probably outwash from the 
Boulder Clay capping of the Essex Plateau. The 
site is about 300 ft. O.D. at Pledgdon Hall Farm, 
in the parish of Henham, on the left bank of the 
brook which flows through Stansted Mountfichet 
into the Stort. I am contemplating further excava- 
tion, with the kind permission of Sir Walter Gilbey, 
the proprietor. I may say that the shallow cutting 
for the new light railway to Thaxted makes the 
stratigraphy of the high ground to the north of this 
minor upland valley quite clear; and there again we 
have evidence of the ‘‘rubble-drift’” movement on the 
hill-slope, of which I have already recorded a good 
number of examples in the Stort Valley. I reserve 
details until the excavation has been carried further. 
Meanwhile, it may be interesting to note here the 
exhumation of a fairly complete skeleton of probably 
a medizeval ox (a ‘‘stray,’’ perhaps, of the time of the 
ancient Essex ‘‘forest-laws’’). The characteristic 
structural features of the skull rank it very closely 
with the type furnished by the remains of Bos from 
Newstead, as described by Prof. J. C. Ewart, F.R.S. 
(“On . Skulls of Oxen from the Roman Military 
Station at Newstead, Melrose,”’ Proceedings. of the 
Zoological Society of London, 1911, text-figure 74), 
while the lower jaw and its dentition present us with 
but a slight modification of those of the Bos primi- 
genius of the glacial shingle of the Stort Valley, at 
the: same time. differing strongly from those of B. 
longifrons (see B.A. Report, loc. cit.). This Essex 
ox-skeleton was cut through by Mr. H. G. Featherby, 
of Bishop’s Stortford, in sinking an iron cylinder on 
the site of a spring for water supply to the farm. 
It was found in what is probably interglacial gravelly 
sand, and beneath some 3 ft. of remanié boulder clay 
stuff, which had worked down (‘rubble-drift ’? again) 
from the Boulder Clay capping of the plateau above. 
It was evidently one of a number of landslides, which 
have furrowed the sloping meadows on both sides of 
the brook at Collier Street Farm, on the Barrington 
Hall Estate, in the parish of Hatfield Broad Oak. 
Bishop’s Stortford, April 27. A. IrvING. 
No. 2218, vot. 89] 
An Anode Dark Space in the Discharge in Oxygen. 
Ir may be of interest to readers of Nature to 
know that I have recently obtained unmistakable 
evidence of an anode dark space in the discharge in 
oxygen at low pressures. The anode which ex- 
hibited this remarkable phenomenon was an 
| aluminium plate which had been used as an anode 
during an extended series of measurements of the 
Crookes dark space with kathodes of different metals. 
As these were continued for some months, and as 
the phenomenon was not noticed when the anode 
was fresh, one is inclined to connect the occurrence 
with the excessive fatigue of the metal surface. 
The anode dark space is a region of comparative 
darkness just in front of the anode, and can only be 
seen when the latter is immersed in the bright nega 
tive glow. Its thickness is small, but as its edge 
is exceedingly sharp, it can be measured with fair 
accuracy. The rough values already obtained are 
very interesting, as they show it to be entirely un- 
affected by changes of pressure and to vary inversely 
as the square root of the current density; with the 
latter at one-tenth of a milliampere per sq. cm., its 
value is about 1-2 mm. in pure oxygen. 
The same anode showed it, though faintly, in air 
and nitrogen, but no trace of it could be observed in 
hydrogen. F. W. Aston. 
Cavendish Laboratory, Cambridge, April 25. 
May Meteor-showers. 
Tue following meteor-showers become due during 
the period May 1-24, their arrangement being accord- 
ing to the times of the principal maxima :— 
Epoch May 3, oh. 30m. (G.M.T.), approximately 
tenth order of magnitude. Principal maximum, 
May 3, 22h. 5om.; secondary maxima, May 3, 
18h, 50m., and May 5, 19h. 4om. 
Epoch May 4, sh., third order of magnitude. 
Principal maximum, May 4, 5h. 10m.; secondary 
maximum, May 4, 17h. 50m. 
Epoch May 8, r1h., twelfth order of magnitude. 
Principal maxima, May 5, 13h. 25m., and May 7, 
toh. 1om.; secondary maximum, May 7, 12h. 20m. 
Epoch May 8, 14h. 30m., approximately fifteenth 
order of magnitude. Principal maximum, May 9, 
13h. rom.; secondary maximum, May 9, oh. 4om. 
Epoch May 12, 23h. 30m., twenty-fifth order of 
magnitude. Principal maximum, May 11, 16h. 15m.; 
secondary maxima, May 9, 19h. 30m., and May 12, 
Epoch May 13, toh., approximately twenty-fifth 
order of magnitude. Principal maximum, May 13, 
15h. 55m., May 14, 23h. 25m., and May 16, 1rh. 45m. 
Epoch May 19, 6h., fifteenth order of magnitude 
Principal maximum, May 18, 17h.; secondary maxi. 
mum, May 18, oh. 55m. 
Epoch May 10, 18h., fourteenth order of magni- 
tude. Principal maximum, May 18, 5h. 30m.-: 
secondary maxima, May 19, 13h. 55m. and 16h. 5m. 
Epoch May tg, 18h., thirteenth order of magnitude. 
Principal maxima, May 19, 20h. 55m., and May 21 
16h. 55m.; secondary maxima, May 21, sh. 45m. and 
12h. 50m. 
Epoch May 21, 22h., second order of magnitude. 
Principal maximum, May 23, 13h. 45m.; secondary 
maxima, May 22, toh. 30m., and May 23, 7h. 30m. 
The intensity of an epoch being inversely as its 
order of magnitude, the greatest meteoric activity 
occurs on May 4 and May 23. The epoch of May 21. 
22h., apart from its high intensity, is a very interest 
ing epoch, and this remark applies also to the double 
epoch of May 10, 18h. 
April 20. Joun R. Henry. 
