704 
prisms. A gun-metal cylinder with its axis normal 
to a triangular brass-plate, about 5 cm. in diameter, 
resting on three screws, one of which has a graduated 
head, is movable vertically along, and rotatable about 
its axis, and by rotation of the graduated screw the 
axis of the cylinder is inclined at a known angle to 
the grinding lap. A crystal suitably mounted is 
brought by means of these two rotations into any 
desired position, a series of chucks of different inclina- 
tions being provided for holding it. The zero position 
is determined optically. A graphical method of deter- 
mining the requisite rotations was described. 
Zoological Society, February 3.—Sir John Rose Brad- 
ford, vice-president, in the chair.—G, A. Boulenger : 
Collections of Batrachians and reptiles made by the 
British Ornithologists’ Union and the Wollaston Ex- 
peditions in Dutch New Guinea. Four species of 
Batrachians and eight species of reptiles were de- 
scribed as new.—Dr. F. E. Beddard: Further observa- 
tions upon the Cestode genus Urocystidium, Beddard. 
Mathematical Society, February 12.—Prof. H. F. 
Baker, vice-president, in the chair.—G. T. Bennett : 
Exhibition and explanation of some models illustrating 
kinematics.—Prof. H. M. Macdonald ; Formulz for the 
spherical harmonic P,-™ («), when 1—, is a small 
quantity.—Prof. E. W. Hobson: The representation of 
the symmetrical nucleus of a linear integral equation. 
—Dr. W. F. Sheppard: Fitting of polynomials by the 
method of least squares (second paper).—H. Bateman : 
The differential geometry of point-transformations 
between two planes.—Major McKendrick: Studies in 
the theory of continuous probabilities. 
MANCHESTER, 
Literary and Philosophical Society, January 27.—Mr. 
F. Nicholson, president, in the chair.—T. A, Coward : 
The willow titmouse in Lancashire and Cheshire. 
The author, after defending the subdivision of geo- 
graphical races of birds into subspecies with distinctive 
trinomials, described how the Holarctic black-capped 
titmice fell naturally into two main groups, having 
as their types Parus palustris and P. atricapillus, L. 
The marsh-tit, the British representative of the first 
group, has long been recognised and accepted, but 
only within recent years has it been discovered that 
a British willow titmouse is referable to the atri- 
capillus group. The willow-tit occurs along with the 
marsh-tit in many English counties, and it apparently 
replaces the latter bird in Scotland. It is found in 
both Lancashire and Cheshire, and in 1913, at any 
rate, nested in Cheshire. Most writers on British 
birds have described the typical marsh-tit, apparently 
in ignorance of the occurrence of both forms. Mac- 
gillivray, whose specimens were obtained in Scotland, 
accurately describes the willow titmouse. Both birds, 
however, are figured and described in the ‘ British 
Bird Book,” edited by F. B. Kirkman.—Dr. A. D. 
Imms ; Observations on Phromnia margineila in India, 
He discussed the recorded instances of insects of the 
Fulgorid genus Phromnia, or Flata, bearing a close 
resemblance to certain flowers. One species, observed 
by J. W. Gregory, exists in two forms, one green and 
one reddish, and he (Gregory) describes the insects so 
grouped on a stem that the green individuals occupy 
the upper portion with the red individuals immediately 
beneath them, thus closely resembling a flowering spike 
with the green unopened buds above. On the occasions 
on which the author observed P. marginella, in the 
Himalayan foothills of Kumaon, the two types—one 
green, the other pinkish-buff—were closely inter- 
mixed.- Poulton suggests that the first specimens of 
a group to emerge are red, and those that issue later 
green. Gregory may have come across undisturbed 
groups which, therefore, had the. green specimens 
NO. 2312, VOL. 92] 
NATURE. 
[FEBRUARY 19, 1914 
above and the red ones below. The groups noted by 
other observers may have reassembled, and thus lost 
the possible arrangement possessed on emergence 
from the pupe. Long waxy filaments, closely related 
chemically to Chinese white wax, 
hinder extremity of the larva of P. marginella. 
DUBLIN. 
Royal Dublin Society, January 27.—Prof. J. Joly, 
in the chair.—Prof. W. Brown and J. Smith: 
Subsidence of torsional oscillations in nickel wires 
when subjected to the influence of alternating mag- 
netic fields. The experiments showed that a remark- 
able decrease takes place in the internal friction of the 
wire when under the influence of alternating magnetic 
fields, the influence being more marked the higher 
the frequency of the alternations. There was shown 
also a very marked difference in the behaviour of the 
nickel wires in the hard and soft states, the hard wire 
after being subjected to an alternating magnetic field 
of high frequency, say 100 to 140 a second, became 
temporarily non-magnetic, which the authors call mag- 
netic fatigue. That this fatigue is temporary is shown 
by the fact that it can be cured in several ways.— 
Prof. T. Johnson: The fouling of a water supply by 
Oscillatoria and its purification. In the spring of 
1913, when the London water supply was contaminated 
by the two diatoms Asterionella and Tabellaria, an 
important water supply in Ireland also suffered from ~ 
the presence of a Myxophycean, Oscillatoria tenuis, 
Ag., var. natans, which gave the storage water (360 
million gallons) a fishy, mouldy smell. The water 
was cleared of the weed without injury to fish or man 
by treating it with copper sulphate (1 to 10 Ib. in 
1,000,000egallons of water), as recommended by Moore 
and Kellerman, of the U.S. Department of Agricul- 
ture. Mud dredged from the shallow bottom of the 
upper end of the storage mountain lake gave the 
‘“water-bloom"’ of writers on examination in the 
laboratory.—Prof. H. H. Dixon: Note on changes in 
the sap caused by the heating of a branch. The 
changes which might be anticipated in the sap of the 
conducting tracts of a branch by the rendering per- 
meable of the plasmatic membranes of the adjoining 
cells and the consequent discharge of their contents 
may be experimentally demonstrated by cryoscopic 
and conductivity measurements, and by various chem- 
ical tests. It is found that sap centrifuged from a 
heated branch is from four to six times more concen- 
trated than that similarly extracted from a living one. 
This change in concentration of substances not rapidly 
absorbed would act as a physical poison on the cells 
of the leaves supported by the branch, and would alone 
explain the changes observed in these leaves. It was 
also found, in four cases out of five, that the sap of a 
steamed branch acted as a protoplasmic poison to the 
cells of Elodea leaves, while during the same time 
the sap from fresh branches was innocuous.—Prof. 
H. H. Dixon: Note on the tensile strength of the sap 
of trees. It has recently been stated that while water 
sensibly free from dissolved air has considerable ten- 
sile strength, it has been impossible to demonstrate 
this cohesion in the sap of trees. This statement is 
negatived by previous experimental work. However, 
it seemed of interest to test the tensile strength of sap 
directly. Experiments were carried out on sap centri- 
fuged from the branches of trees. Berthelot’s method 
of generating tension was used, but allowance was 
made for the distortion of the containing tube during 
the experiment. It was found easy to generate ten- 
sion in both boiled and unboiled sap. In both cases 
the sap was almost; if not quite, saturated with dis- 
solved air. The highest tension obtained with the 
boiled sap was 72:5 atmospheres, but with the un- 
boiled 208 atmospheres was obtained.—Prof. J. Joly : 
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