Fuly 22, 1886] 
NATURE 
283 
SOCIETIES AND ACADEMIES 
LONDON 
Physical Society, June 26.—Prof. W. E. Ayrton, F.R.S., 
Vice-President, in the chair.—Mr. E. M. Langley was elected 
a Member of the Society. —The following communications were 
read :—On certain sources of error in connection with experi- 
ments on torsional vibrations, by Mr. Herbert Tomlinson. 
During a long series of researches on the torsional elasticity and 
internal friction of metals, the author has come across the fol- 
lowing sources of error in connection with torsional vibrations. 
In some of the earlier experiments a horizontal brass bar was 
suspended by a wire and oscillated, the times of oscillation 
being observed by the ordinary lamp, mirror, and scale. The 
moment of inertia was varied by sliding two brass cylinders, 
suspended from the bar by fine wires, backwards and forwards 
along it. It was then found that under certain conditions the 
bar executed a few vibrations of rapidly decreasing amplitude, 
came to rest, and then commenced to swing again, the ampli- 
tude increasing to a maximum, again decreasing, and so on. 
This effect was finally traced to an approach to synchronism 
between the time of oscillation of the bar and that of the 
small cylinders about their axes of suspension, the absorption 
of energy being due to these being set in vibration. The effect 
entirely disappeared upon clamping the cylinders rapidly to the 
bar. On another occasion, however, the old phenomenon re- 
appeared, and after much time spent in investigating it, was 
_ found to be due toa somewhat similar cause, a near approach 
to synchronism between the periods of torsional and pendulous 
vibrations. If the axis of the wire passed accurately through the 
centre of mass of the vibrator, this would not occur ; and this condi- 
tion it is practically impossible to fulfil. Another source of error 
lies in the fact that, in a wire recently suspended, the torsional 
vibration-period will always be found to be slightly greater than 
when it has been suspended for some time and frequently oscil- 
lated. —On a mode of driving electric tuning-forks, by Prof. S. 
P. Thompson. It is invariably found that the frequency of an 
electrically maintained fork is continually changing. This great 
inconvenience the author believes to be due to the fact that the 
impulses are given to the prongs at a disadvantageous moment, 
namely, when they are at the extremities of their swings. It is 
desirable that the impulse should be given at the middle of the 
swing, and to effect this it is suggested that each fork should 
make and break the circuit of the magnet influencing the other 
one, and it was shown how the electrical connections could be 
made to effect this in a simple manner.—Prof. Silvanus P. 
Thompson then read some further notes on the formulz of the 
electro-magnet and of the dynamo. The author pointed out that 
_a misapprehension of his former paper on this subject had given 
rise to certain critical remarks by Dr. O. Frohlich, to which he 
replied. The author also explained the new form given recently 
by Dr. Frohlich to the formula of the electro-magnet, rendering 
I much more readily applicable to the various equations of 
_ dynamo-machines. Formerly the Lamont-Frohlich formula had 
_ been written— 
m= M ee 7 
I + kx 
| 
} 
} where JZ and & are constants, and x the magnetising force. Dr. 
_ Frohlich now suggested a formula of the form— 
x 
Ta 
> 
x+ x" 
where Y is the maximum value of 7, and where x is either the 
current or the potential applied to the electro-magnet, and «’ the 
diacritical value of the same; the ‘‘diacritical” value, as 
defined by the author in 1884, being that value which produced 
the state of half-saturation of the magnetic circuit. The author, 
_ folowing the lines laid down by Frohlich in the use of this equa- 
tion, showed that the general equation of the self-exciting 
dynamo is necessarily of the form 
y=¥-vV, 
where y is either current or potential, y the “ diacritical” value 
f the same, and ¥ the ‘‘ maximal” value of the same ; that is 
0 say, is the value which w would have if the given machine 
were run at the given speed and with the given internal and 
external resistances, but having its magnets independently 
excited to absolute saturation. Further deductions concerning 
the ‘“dead turns” of the dynamo, their independence of speed, 
and dependence upon the resistances of the circuit and upon the 
construction of the machine were shown. 
SYDNEY 
Linnean Society of New South Wales, April 28.— 
Prof. W. J. Stephens, F.G.S., President, in the chair.— 
The following papers were read:—On some Lepidoptera from 
the Fly River, New Guinea, by E. Meyrick. Mr. Meyrick’s 
paper contains an account of the Lepidoptera (Heterocera), col- 
lected by the recent New Guinea Expedition. Specimens of 
twenty-five species were met with, of which fifteen appear to be 
new, and are described by Mr. Meyrick. Nearly all :of these 
may be said to be of normal Indo-Malayan types. A few speci- 
mens, from their bad condition, were unidentifiable or unfit for 
description.—Catalogue of the described Coleoptera of Australia, 
part 4, by George Masters. This part contains the names of, 
and refezences to, all the known species of the families—7)zxa- 
gide, Eucnmide, Elateridi, Cebrionide, Rhipidoceride, Dascil- 
lide, Malacodermide, Cleride, Lymexylonide, Cupeside, Ptin- 
ide, Cwide, Bostrychide, Tenebrionide, Cistelide, P)thide, 
Monommatide, Mdandryide, Lagrude, Vedilide, Anthicide, 
Pyrochroide, Mordellide, Rhipidophoride, Cantharide, and 
GQdemeride, numbering 1494 species.—Miscellanea Entomo- 
logica, by William Macleay, F.L.S. This is the first of a series 
of papers descriptive of some of the new or rare Coleoptera in 
the Macleay Museum. The intention of the author is to 
accompany these de-criptions with a general review of the 
genera or groups dealt with. The present paper is a revision of 
the genus Diphucephala, to which oyer twenty new species are 
added.—A revision of the Staphylinidz of Australia, part 1, 
by A. Sidney Olliff, Assistant Zoologist, Australian Museum. 
The object of this paper is to furnish entomologists with descrip- 
tions of all the Australian Staphylinidz at present known, to 
summarise the characters of the genera, and to make known a 
number of new forms. ‘This first part contains the sub-family 
Aleocharine, of which the tribes Aleocharina, Gyrophzenina, and 
Gymnusina are all represented. Among the most remarkable of 
the new forms belonging to the first of these tribes is a species 
from New South Wales described under the name Apphianie 
veris (gen. et sp. noy.), and characterised by having the basal 
joints of the antennze enormously dilated on the outer side ; the 
second joint being twice as broad as long, the third equally 
broad, but shorter, the fourth, fifth, and sixth shorter and 
gradually decreasing in breadth. In facies the species resembles 
a Pelioptera.—Notes from the Australian Museum, by E, P. 
Ramsay, F.R.S.E., and J. Douglas Ogilby. Two species cf 
fish are described in this paper—JZyripristis carneus, from the 
Admiralty Islands, presented to the Australian Museum by Capt. 
Farrell, and Sygvathus parviceps, from the Clarence River dis- 
trict, presented by Mr. Temperly, Inspector of Fisheries. —The 
Hon. James Norton exhibited a number of fossils (Chzetetes and 
Spirifers) from Black Head, a few miles south of Kiama. 
Also, specimens of a porphyritic rock from Coolangatta, Shoal- 
hayen, with the large crystals present in some, and decomposed 
by weathering in others.—Mr. Whitelegge exhibited specimens 
of a large species of Vite//a with the following explanatory note. 
““ A short time ago I found in the Parramatta River a very re- 
markable member of the above genus. It is an erect growing 
plant between 3 and 4 feet in height, mostly branching near the 
base, and giving off some five or six whorls of simple leaves, 
each leaf consisting usually of three cells, sometime of only two. 
The stem and leaves (six in number) are usually about 4; of an 
inch in diameter. The internodal cells of the stem are usually 
4 or 5 inches, but sometimes much longer. I have measured 
some of the largest yet found, and they are from 7 inches up to 
84 long. It is highly probable that the cells of this plant are 
larger than those of any hitherto recorded. There are several 
other features which may not have been noticed in the genus. 
For instance, the leaves can be realily disarticulated from the 
stems without any apparent injury to either. When a cell is 
ruptured the sound produced is not unlike that of the bursting of 
the air-bladders of seaweeds. The rotation exhibited in the 
inner nodal cells differs from that of the stem and leaves, inas- 
much as the chlorophyll granules take part in the general rota- 
tion. The protoplasm in the young leaves, when viewed under 
the microscope with the edge of the cell in focus, appears as a 
series of elevations and depressions, and with the higher part of 
the cell in focus, these elevations appear as clear spaces sui- 
rounded by small granules. Within the layer of protoplasm 
there exist large numbers of spherical clusters of needle-like 
