
Dee. 15, 
1870] 
NATURE 
135 

structor, is ready to meet the difficulties, but he was not willing to 
avoid them at once by having a more simple scheme to work out. 
It is so much the more to be wondered at, if this clever aéronaut 
has not adopted this policy, inasmuch as he does not profess to 
go against the wind, but to design a contrivance which may help 
aéronauts in using the wind for a certain purpose, as returning 
to Paris froma town located at some distance, as Lille, Le Mans, 
&c. M.Dupuy de Lome intends to attain the desired result 
by making a definite angle with the direction of the reigning 
wind, which supposes on the part of the aéronaut some previous 
knowledge of the state of atmospheric currents, their change 
of duration, and different directions at different elevations ; 
the principal feature of his intended directing balloon being 
the grand idea of having the motive power like an auxiliary im- 
plement for giving to the balloon differential motions. It does 
not, of course, prevent the aéronaut from using the deflections 
and variations of the wind according to the elevation of his 
balloon at any moment. The working out of these aérial 
manceuvres supposes necessarily that aérial navigators can know 
at any moment the place where they are. It requires constant 
_ attention from the aérial travellers, who are supposed to 
be supplied with every possible instrument for looking over 
the land and finding the places on the map prepared for that 
very purpose. It would be of itself a most interesting chapter, 
the better construction of such maps, as well as the determina- 
tion of the means by which public authorities could give 
warnings to the aérial travellers. But in the present state 
of things, I should not be justified if I did not abstain from giving 
details which may prove useful to the invaders of my native 
Jand. I will be satisfied with saying, moreover, that the taking 
of the point in sailors’ fashion is quite out of the question. The 
only condition is the view of the land remaining always at the 
command of the observer, or only being lost for short intervals, 
during which more than the usual attention is required. I have 
invented an apparatus called an aérial planchette, for helping 
aéronauts in the determination of their way, but from the ex- 
perience of my last excursion I have lost every confidence in my 
instrument. I think that it is quite useless; the only thing 
_ required being good maps and better eyes, helped by powerful 
opera-glasses. The power of these can be enlarged by a very 
simple contrivance, which I mention merely to show that I know 
what is still to be done in this respect. 
The question of the motive power to be employed is not of 
so much importance as was supposed at the first instance; and it 
is very easy to understand why, admitting that we want only a 
slow motion. I should not object, of course, to a quick displace- 
ment ; but I am satisfied it cannot be obtained except by con- 
trivances very difficult to imagine, and even more to realise, 
and besides it is not required for the special purpose in view, the 
returning to Paris from a French city which German armies 
have not occupied. The rate of motion will be improved by 
degrees, and will not amount to a large increase, except by the use 
of steam engines, which requires a great many preliminary steps 
to prevent the gas of the balloon from being lighted by the 
fire from the furnace, which would lead to the destruction of the 
balloon and of the aéronauts. The simplest contrivance will be 
the best if it proves useful. I should advise to arrange the 
motor apparatus so that it could be used by hand, and, be- 
sides, that it could be very easily thrown overboard like ballast 
in case of need. These two conditions being of much importance 
for our purpose, if I start for Paris, which I hope will be the 
case, I shall adhere strictly to them. 
I have no objection to use a rudder, which may be constructed 
in a manner very easy to understand, but I should feel very 
much disposed to dispense with it. I think that a propelling 
machine may be arranged so that no rudder at all will be put 
into operation. Iam afraid to give moré substantial explana- 
tions, which could hardly be offered without giving a full know- 
ledge of my intended construction, which is not my purpose. 
The contributions of M. Dupuy de Lome to the Comptes 
rendus, have been sharply commented upon by the Aeronaut, 
a special paper devoted to the aérial navigation worked out by 
the plus lourd que Vair system, as inaugurated by Lalandelle and 
Nadar, and many other gentlemen of very little or no scientific 
qualifications. But every scientific man must confess that these 
interesting papers constitute by themselves a very valuable acqui- 
sition to general knowledge, independently of their special 
aim. M. Dupuy de Lome has given at the same time many 
calculations to show to what elevation a given balloon can attain 
under the conditions he has adopted, viz., constant fulness, 

and a certain excess of internal pressure for giving it a stability 
of form and of equilibrium. 
Without quoting M. Dupuy de Lome’s paper, and even cor- 
recting some parts of it, I will give a rough idea of the analytical 
questions involved in the calculation of the circumstances of an 
acrostatical ascent. I suppose, firstly, that the air has no horizontal 
movement at all, and that the only questions are to ascertain the 
elevation which the balloon may reach, the time that may be 
required, and the velocity with which the balloon ascends at the 
various points of its vertical course, as well upwards as down- 
wards. There are besides two accessory suppositions which are 
required. The firstis, that the balloon does not lose its gas by 
any exosmose during the experiment ; and the second is that the 
temperature of the air, as well as the degree of moisture, is not 
altered inany degree. These conditions are hardly to be expected, 
but they are required for mathematically working out the 
analytical equations. 
M. Dupuy de Lome, however, would not have been placed in 
a position to proceed with his calculations, if he had not very 
cleverly evaded the consideration of the other conditions, which 
are insuperable, owing to our imperfect knowledge of the atmo- 
sphere, as we shall see hereafter. W. DE FONVIELLE 


PROF, WILLIAMSON’S INAUGURAL LECTURE 
TONVEREEE NEP AGUIED Van (OLS CHEN Gia ers 
UNIVERSITY COLLEGE, LONDON 
"THE great value of scientific knowledge asa means of cul- 
ture, a promoter of civilisation, and one of the most 
powerful levers of national prosperity, seems at least to receive 
its due acknowledgment in the land of Bacon and Newton, 
Sir Humphry Davy and Faraday. The recent efforts to intro- 
duce science into the public schools of England appear as a 
consequence of this recognition. A great variety of opinion, 
however, exists as regards the mode by which scientific knowledge 
ought to be imparted to the people. Some believe that a young 
farmer ought to be taught agricultural chemistry, the man at the 
furnace the chemistry of iron melting, and the maker of colours 
the chemistry of colours, This is what is called by many “ techni- 
cal education,” for the promotion of which great efforts have 
been made of late. Technical education in this sense would be 
a mistake. It would not be difficult to show that it is impossible 
to teach, with any considerable effect, agricultural chemistry, 
which is the application of certain chemical principles to Agri- 
culture, without a knowledge of these principles. These, with 
others, form part of the science of Chemistry, and it is clearly 
absurd to isolate them and teach their application in some par- 
ticular case. The working classes of England want a knowledge 
of the elements of pure science ; and they are sure to make use- 
ful application of this knowledge as soon as an opportunity 
offers itself. In this sense Professor Williamson expresses himself 
in his admirable lecture, ‘‘ A Plea for Pure Science,” * which on 
account of its sound views on some of the most important 
questions of the day, we recommend to the attention of our 
readers. On p. 3 Prof. Williamson says, ‘‘ Now there are in edv- 
cation two great national parties, corresponding to the two most 
different points of view from which the preparation cf any young 
person for his career in life can be considered. I submit that 
the progress of education will be proportional to the consistency 
and completeness with which the functions of these two parties 
are systematised and developed. 
“ The first step towards that object is to know and acknowledge 
their respective characteristics. ' ' 
“One party looks to the special duties for which a young person 
has to be prepared and the material difficulties which he is ex- 
pected to encounter. They see that the success and happiness 
of each individual are proportional to the efficiency with which 
he discharges the aggregate of the special duties of his station in 
life ; and they accordingly recommend that each youth be placed 
in circumstances which may induce him to imitate accurately the 
doings of some one who is known to be successful in a station 
such as he is intended to occupy. The other party looks to the 
general qualifications which experience has shown to be most 
important for any success in life; and to the means by which 
they are most effectually acquired, They see that men who 
have been taught to understand and apply the best-known general 
principles are able to master a given set of practical details with 
a facility and completeness which other men do not attain. They 
know that a general principle of nature is an instrument of 
* “4 Plea for Pure Science.” By A. W. Williamson, Ph.D., F.R.S. 
