406 
NATURE 
[FEBRUARY 25, 1904 
into their system of.education the principles and. methods of 
science,’’ and goes on to urge that the universities can do 
much to promote and encourage improvement in these 
matters. It is suggested that the universities might ex- 
pand and improve their general tests, so as to make these 
correspond with the education, both literary and scientific, 
which a student, matriculating at the age of nineteen years, 
should be expected to have acquired. Commenting on these 
communications from the Royal Society, Prof. Case, in a 
letter to the Times, remarks ‘‘ that the real contention is 
that while Greek is not, ‘ science’ is, an essential part of 
general education.’’ But as his letter shows, Prof. Case 
means by “ science ’’ some single subject such as mechanics, 
whereas the Royal Society is pleading for instruction in the 
methods of science. It may fairly be asserted that no 
general education can be complete in which scientific method 
takes no part; yet, in the past, there has been a compulsory 
examination in Greek and none in science. Though men 
of science do not ask for compulsory examinations in single 
subjects of science, nor advocate these as essential parts of 
the school curriculum, yet they urge strongly that the spirit 
of scientific observation and inquiry should be fostered 
because it promotes both the material and the intellectual 
progress of the nation. 
SOCIETIES AND ACADEMIES. 
Lonpon. 
Royal Society, June 18, 1903. (Received in revised form 
January, 1904.)—‘* The Longitudinal Stability of Aérial 
Gliders.”” By G. H. Bryan, Sc.D., F.R.S., and W. E. 
Williams, B.Sc., University College of North Wales. 
The object of the investigations was (1) to show that the 
longitudinal stability of aéroplane systems can be made the 
subject of mathematical calculation ; (2) to direct the atten- 
tion of those interested in the problem of artificial flight to” 
the necessity of acquiring further experimental knowledge 
concerning the quantities on which this stability is shown 
to depend. 
The conclusions reached were as follows : 
(1) For a glider or other body moving in a vertical plane 
in a resisting medium of any kind whatever, the small 
oscillations about a state of uniform rectilinear motion are 
determined by an equation of the fourth degree, so that the 
conditions for stable steady motion are those obtained by 
Routh. 
(2) The coefficients in the period equation involve, in 
addition to the ordinary dynamical constants, nine quanti- 
ties X, . . G% which, when referred to rectangular axes 
fixed in the body, represent the differential coefficients of the 
forces and couple due to the aérial resistances with respect 
to its translatory and rotatory velocity components. 
(3) In the case of a system of aéroplanes these nine quanti- 
ties can be expressed for the separate planes in terms of 
f(a) and (a), where f(a) and (a) are functions deter- 
mining the resultant thrust, and the position of the centre 
of pressure when the direction of the relative motion of the 
air makes an angle @ with the plane. These functions have 
been tabulated for certain different forms of surfaces, but 
further data are greatly needed. 
(4) The longitudinal stability of the gliders is thus seen 
to be capable of mathematical investigation, and it is of 
paramount importance that the present methods should be 
practically applied to any aérial machines that may be de- 
signed or constructed before any actual glides are attempted. 
(5) The methods of calculation are exemplified by 
numerical determinations of the criterion of stability in the 
cases of a single plane lamina, and a pair of planes one 
behind the other. Most of the calculations have been per- 
formed for an angle of gliding of 10° with the horizon, and 
it has been necessary to assume arbitrary values for the 
moment of inertia of the lamina. ‘ 
(6) The condition that any steady linear motion may be 
stable in all these cases assumes the form V2>ka, where 
a is a constant depending on the linear dimensions of the 
glider, and k is a constant depending on its shape, the 
angle of gliding and the law of aérial resistance. 
(7) For a pair of narrow slats, in which the variations 
in the positions of the centres of pressure of each are 
NO. 1791, VOL. 69] 
_ istic of each *‘ biologic form,’ 
| sharply defined and fixed. 
| periments of numerous investigators—both with regard to 
neglected, certain coefficients of stability vanish. if. the slats 
are in the same plane. If the planes are square so that the 
displacements of the centres of pressure are not neglected, 
the system is in general less stable than a single square 
plane. < 
(8) By inclining the planes at a small angle to each 
other the stability is much increased. On the other hand, 
if they are made to slope away from each other, the glider 
becomes unstable. 
(9) Two square planes of equal size placed one behind the 
other at a small angle are less stable in the examples con- 
sidered than a square of the same size as one of the two, 
but more stable than a single square the side of which is 
equal to the total length of the glider formed by the pair. 
(10) A pair of unequal squares of which the smaller forms 
a rudder are more stable, in the examples considered, when 
gliding with the rudder behind than with the rudder in 
front. 
(11) In the examples considered stability is increased by 
decreasing the moment of inertia of the glider. 
February 4.—‘ Cultural Experiments with ‘ Biologic 
Forms’ of the Erysiphacew.’’ By Ernest S. Salmon, 
F.L.S. Communicated by Prof. H. Marshall Ward, F.R.S. 
The author points out that through specialisation of 
parasitism ‘‘ biologic forms’’ have been evolved in the 
Erysiphaceee, and that the powers of infection, character- 
’ are under normal conditions 
Hitherto the result of the ex- 
the present group of fungi and to the Uredineaze, where the 
same specialisation of parasitism occurs—has been the 
accumulation of evidence tending to emphasise the immuta- 
bility of *‘ biologic forms.”’ 
In a series of cultural experiments with ‘* biologic 
forms ’’ of Erysiphe Graminis, DC., the author has dis- 
covered that under certain methods of culture, in which the 
vitality of the host-leaf is interfered with, the restricted 
powers of infection, characteristic of ‘‘ biologic forms,’” 
break down. 
In these cultural experiments the leaf, previous to in- 
oculation, was injured by the removal of a minute piece of 
leaf-tissue, or by touching the epidermis with a red-hot 
knife. The experiments proved that the range of infection 
| of a ** biologic form ’’ becomes increased when the vitality 
of a leaf is affected by injury, so that the conidia of certain 
“biologic forms ’’ are able to infect injured leaves of host- 
species which are normally immune against their attacks. 
Further experiments showed that the conidia of the fungus 
produced on a ‘“‘cut’’ leaf are able at once to infect un- 
injured leaves of the same host-species. 
The author suggests that injuries to leaves, caused in 
nature by hail, storms of wind, attacks of animals, &c., 
may produce the same effect as the artificial injuries de- 
scribed above in rendering the injured leaf susceptible to 
a fungus otherwise unable to infect it. 
Attention is directed to the close parallel between. the 
behaviour of the fungus in the experiments and the bio- 
logical facts obtaining in the class of parasitic fungi known 
as ‘‘ wound parasites ’’ (Nectria, Peziza willkommii, &c.). 
“On the Effects of Joining the Cervical Sympathetic 
Nerve with the Chorda Tympani.’’ By J. N. Langley, 
F.R.S., and H. Kk. Anderson, M.D. 
The experiments have been directed to determine whether 
the cervical sympathetic, if allowed an opportunity of be- 
coming connected with the peripheral nerve cells in the 
course of the chorda tympani, will in part change their 
function from  vaso-constrictor to vaso-dilator. The 
superior cervical ganglion in an anzesthetised cat was ex- 
cised and the central end of the cervical sympathetic nerve 
was joined to the peripheral end of the lingual, which 
contains the chorda tympani fibres. After allowing time 
for union and regeneration of the nerves, the cervical 
sympathetic was stimulated; it caused prompt flushing of 
the sub-maxillary glands, and the effect was repeatedly 
obtained. 
The experiment shows (1) that vaso-constrictor nerve 
fibres are capable of making connection with peripheral 
vaso-dilator nerve cells, and becoming vaso-dilator fibres, 
and (2) that whether contraction or inhibition of the un- 
