414 
NATURE 
[ Feb. 17, 1870 
smaller ; at a certain velocity, bearing a definite relation to the 
length of the model, the resistances became equal; at higher 
velocities, the round-ended model had a rapidly increasing advan- 
tage over the sharp-ended model. 
Hence it appeared to the author to be desirable to investigate 
the mathematical properties of stream-lines resembling the water- 
lines of Mr. Froude’s bird-like models. He has found that end- 
less varieties of such forms, all closed curves free from discon- 
tinuity of form and of motion, may be obtained by using four foci 
instead of two. They may be called from this property guadrifocal 
stream-lines, or, from the idea that suggested such shapes to Mr. 
Froude, Cycnoitds ; that is, swan-like lines. * 
Those lines are not to be confounded with the lines of a yacht, 
having at a distance the appearance of a swan, which was 
designed and built some years ago by Mr. Peacock, for the 
figure of that vessel is simply oval. The paper contains four 
chapters. The first three are mainly cinematical and geometri- 
cal, relating to the forms of stream-line surfaces in two and in 
three dimensions, especially those with more than one pair of 
foci and surfaces of revolution—the method of constructing 
graphically and without calculation (by means of processes first 
applied to lines of magnetic force by Mr. Clerk Maxwell) the 
traces of such surfaces, which methods are exemplified by 
diagrams drawn to scale—the motions of the particles of liquid 
past those surfaces. The fourth chapter is dynamical ; it treats 
of the momentum and of the energy of the disturbance in the 
liquid, caused by the progressive motion of a solid that is 
bounded by a ship-shape stream-line surface of any figure what- 
soever—the ratio borne by the total energy of the dis- 
turbance in the liquid to that of the disturbing body when 
that body displaces a mass of liquid equal to its own mass, which 
ratio ranges in different cases from 4 to 1—the acceleration and 
retardation of ships as affected by the disturbance in the water— 
the use of experiments on the retardation of ships in finding 
their resistance—the disturbances of pressure which accompany 
the disturbances of motion in the liquid. Up to this point, the 
dynamical principles arrived at in the fourth chapter are certain 
and exact, like the geometrical and cinematic principles in the 
three preceding chapters. The results obtained in the remainder 
of the fourth chapter are in some respects approximate and con- 
jectural, being to a great extent designed to suggest plans for future 
experiments and rules for their reduction. These results relate to 
the disturbance of level which accompany the disturbances of 
motion, when the liquid has a free upper surface—to the waves 
which originate in those disturbances of level and to the action 
of those waves in dispersing energy and so causing resistance to 
the motion of the vessel;—to friction, or skin-resistance and to 
the ‘*wake”’ or following current which that kind of resistance 
causes the disturbing solid body to drag behind it—lastly, to the 
action of propelling instruments in overcoming different kinds of 
resistance. The resistance caused by viscosity is not treated of, 
because its laws have been completely investigated by Mr. 
Stokes, and because, for bodies of the size of ships, moving at 
their ordinary velocities, that kind of resistance is inconsiderable 
compared with skin-resistance and wave-resistance. ‘The re- 
sistance caused by discontinuity of figure is stated to be analogous 
in its effects to friction; but it is not investigated in detail, be- 
cause ships ought not to be built of discontinuous (commonly called 
“unfair”) figures. In a supplement the author calls attention 
to the agreement between the position of the points at which 
there is no disturbance of the pressure on the surface of a sphere, 
as deduced from Dr. Hoppe’s investigation, published in 1856 
(Quarterly Journal of Mathematics), or on the surface of a short 
vertical cylinder with a flat bottom, as determined by the experi- 
ments of the Rev. E. L. Berthon before 1850 (Proc. Roy. Soc. 
vol. v. 1850 ; also, ‘* Transactions of the Society of Engineers,” 
6th December, 1869. The theoretical value of the angular 
distance of these points from the foremost pole of the sphere is 
sin ~13=41° 49’; the value deduced from the experiment is 
41°30’. The author then adds some remarks on a suggestion 
made by Mr. William Froude, that the wave-resistance of a ship 
is diminished when two series of waves originating at different 
points of her surface partially neutralise each other by inter- 
ference ; stating that, with regard to this and many other questions 
of the resistance of vessels, a great advancement of knowledge 
is to be expected from the publication in detail of the results of 
experiments on which Mr, Froude has long been engaged, 
Zoological Society of London, February 10.—Mr. John 
Gould, in the chair. The secretary stated the principal 
* Kuxvoediye. 
additions to the society’s menagerie during January, amongst 
which was a specimen of the Great Northern Diver (Colymbus 
glacialis), captured in Cornwall, and presented to the society by 
A. R. Hunt, Esq,—A letter was read from Mr. W. H. Hudson, 
of Buenos Ayres, containing some observations on the ornitho- 
logy of La Plata,.—A communication was read from Mr. R, 
Swinhoe, describing a new deer from China, which Mr. 
Swinhoe regarded as constituting a new genus of the family 
Cervide, distinguished by the large canines and the entire want 
of horns in both sexes. This deer was stated to be common on 
the islands on the lower part of the river Yangtze-Kiang near 
Ching-Kiang, and to be often brought into the market of that 
city, but appeared hitherto to have escaped the observation of 
naturalists. Mr. Swinhoe proposed to call it Hydvofpotes inermis. 
—A communication was read from Mr. George Gulliver, on 
the size of the red corpuscles of the blood of Afoschus, Tra- 
gulus, Orycteropus, Adlurus, and some other mammalia, to which 
were added some historical notices relating to the same subject. 
—A communication was read from Surgeon Francis Day, 
containing the second portion of his paper on the fishes of 
Burmah.—The Rey. O. P. Cambridge communicated a mono- 
graph of the genus /diops belonging to the family Mygalides, in 
which were included descriptions of three species eonsidered to 
be new to science. — A communication was read from Mr, 
ohn Brazier, containing descriptions of three new species 
of shells from the Australian coast belonging to the genera 
Voluta and Conus.—Mr. Henry Adams communicated a descrip- 
tion of a new species of mollusk of the genus Co/ws from the 
L’Agulhas Bank, Cape of Good Hope, which he proposed to 
call Colus ventricosus. 
Ethnological Society, February 8.—Dr. A. Campbell in 
the chair, The following new members were announced : Sir 
Charles Wentworth Dilke, Bart., M.P., Rev. A. S. Farrar, 
Messrs. M. C. Fisher, F. R. Munton, and F. B. Wright. ‘On 
some flakes of flint and chert discovered in the angular detyitus 
beneath a submerged forest at Porlock and Minehead in West 
Somerset.” Mr, Boyd Dawkins. These objects of human 
workmanship prove that man must have lived on the old land- 
surface before the destruction of the forest, and the accumulation 
of the series of overlying deposits. It has been supposed that 
this detritus was of glacial age; but the author doubts this. He 
believes, however, that there is evidence to show that the latest 
date which can be assigned to these remains is an early stage in 
the Neolithic period, Dr. Richard King, Colonel Lane Fox, 
Rev. Dr. Nicholas, and Mr. McLennan spoke upon this commu- 
nication. —The Chairman then read some notes introductory to 
a paper on the remains of prehistoric man in the neighbour- 
hood of the Crinan Canal in Argyleshire. This canal is 
nine miles in length, and connects Loch Fyne with Loch 
Crinan. The Rey. Mr, Mapleton described with great precision 
the prehistoric remains in this locality, among which the most 
curious were some peculiar cup-shaped cavities and concentric 
rings rudely sculptured on certain stones. In addition to these 
petroglyphs, there are many menhirs, and numerous cairns of 
various forms: crannoss occur in most of the lochs, but are 
usually merely solitary dwellings. Several duns, a vitrified fort, 
a brough, and a flint-manufactory are also among the remains in 
this district, The Rey. Dr. Nicholas and Colonel Lane Fox 
made some remarks upon this paper.—The assistant-secretary 
exhibited and described a stone hammer-head found by Mr. R, 
Mouat in the old workshop of a copper-mine in Portugal. 
Entomological Society, February 7.—Mr. A. R. Wallace, 
president, in the chair.— Mr. Bates, Major Parry, and Mr. 
Pascoe were nominated as vice-presidents. It was announced 
that the council offered two prizes of the value of five guineas 
each, for essays of sufficient merit, drawn up from personal 
observation, on the anatomy or economy of any insect or insects. 
The essays to be sent in before the end of November next.— 
Mr. Bond and Prof. Westwood exhibited several butterflies, the 
colouration of each being partly that of the male and partly that 
of the female character. Mr. Bond, on behalf of Dr. Wallace, 
exhibited cocoons from various parts of the world, of Boméyx 
Yamamat and Antherea Pernit. Mr. Stainton exhibited a 
large box full of AZicro-Lepidoptera, each specimen being sepa- 
rately labelled to show the locality and date of capture. Mr. 
Bond exhibited some more specimens of Acridium peregrinum, 
from Plymouth ; Mr. Fred. Smith made some observations upon 
the Locusta migratoria of Linné, and Z. Chrestii of Curtis. 
Prof. Westwood exhibited a new form of Cyzipide, from the Sula 
