feb. 1, 1883] 
NATURE 
eye) 
appear to have acted wisely in asking Mr. Philip Magnus, 
who has directed the work of the Institute up to the 
present time with so much ability, and whose exceptional 
experience of Continental technical schoels renders him 
particularly fitting for such a position—to occupy this 
post, pending the completion of the Central Institution, 
and to carry into effect the general scheme of instruction 
indicated in the programme. 
In the day school of the Finsbury College, pupils from 
middle class and higher elementary schools will have the 
opportunity of continuing their studies, and of preparing, 
at the same time, for the particular branch of industry in 
which they purpose to be engaged. 
Such a school is a technical school in the true sense of 
the word, for it gives the pupil the best training he can 
receive for his future occupation. 
The instruction is not limited to the application of one 
branch of science only; the future electrician is taught 
chemistry and mechanics, the chemist is taught mechanics 
and physics, the mechanician is taught physics and che- 
mistry, and, what is almost equally important, all are 
taught drawing, French, German, and the manipulation 
of toals in the workshops. 
The evening school is intended for those who are 
already engaged in practical work, and in this depart- 
ment of the College noteworthy changes have been 
introduced, with a view of adapting the teaching to 
the special requirements of artisans. To the courses 
of Applied Physics and Chemistry originally provided 
for, courses of Mechanical Engineering have been 
added; but besides these courses, which are adapted to 
the higher class of artisans, a complete syllabus of in- 
struction has been added to the programme, suited to the 
requirements of the special industry of the district of 
Finsbury, viz. cabinet-making. To provide a systematic 
course of instruction for cabinet-makers it was necessary 
to add to the other departments of the College, a Depart- 
ment of Applied Art; and in order to secure a good 
number of students to start with, the Council affiliated 
to the College the City School of Art, one of the oldest 
art schools of the country, and appointed Mr. Brophy as 
head master. 
Moreover, to satisfy the demand of workmen engaged 
in numerous small industries, the Council have arranged 
courses of instruction, on a more systematic basis than 
has been previously attempted in this country, for car- 
penters, joiners, metal-plate workers, bricklayers, &c., 
thereby supplying that popular element in the instruction 
provided by the City Guilds, which at first seemed likely 
to be wanting in their scheme of technical education. 
By undertaking to admit apprentices to the evening 
classes at half the fees, which are small enough, charged 
to ordinary workmen, those who have had the direction 
of the work of the Institute have shown a just appreciation 
of the importance of encouraging apprentices of fifteen to 
twenty to follow the evening courses of instruction ; for 
there will be far less difficulty in inducing youths, during 
their apprenticeship, to attend regular systematically- 
arranged lessons, covering a period of two or three 
years, than is generally found in the case of adult 
workmen. 
Indeed, it is in the arrangement of systematised and 
progressive courses of instruction adapted to various 
industries and involving the application both of science 
and of art to the student's occupation, as well as in the 
practical methods of instruction adopted, that the Techni- 
cal College, Finsbury, is differentiated from other science 
schools. 
The programme of studies now before us is a publica- 
tion that can hardly fail to prove useful to all persons who 
are interested in the establishment of technical schools, 
and shows unmistakably that the Council of the Institute 
and their advisers are fully conscious of the difficulties 
that beset the problem of technical education, and may 
be trusted to deal judiciously with them in the schools 
established under their direction. 
The fittings of the new College, which are most com- 
plete and admirably adapted for practical teaching, have 
been designed and executed under the direction of 
Professors Armstrong, Ayrton, and Perry. 
ON THE GRADUATION OF GALVANOMETERS 
FOR THE MEASUREMENT OF CURRENTS 
AND POTENTIALS IN ABSOLUTE MEASURE* 
III. 
HE determination of 7 and the measurement of a 
current in absolute units, can be effected simul- 
taneously by the method devised by Kohlrausch, and 
described in the Philosophical Magazine, vol. xxxix. 1870. 
This method consists essentially in sending the current 
to be measured through two coils, of which all the con- 
stants are accurately known. One of these is the coil of 
a standard galvanometer, the other is a coi] hung by a 
bifilar suspension, the wires of which convey the current 
into the coil. The latter coil rests in equilibrium when 
no current is passing through it, with its plane in the 
magnetic meridian. When a current is sent through it, 
it is acted on by a couple due to electro-magnetic action 
between the current and the horizontal component of the 
earth’s force, which tends to set it with its plane at right 
angles to the magnetic meridian; and this couple is 
resisted by the action of the bifilar. The coil comes to 
rest, making a certain angle with the magnetic meridian, 
and as the couple exerted by the bifilar suspension for 
any angle is supposed to have been determined by experi- 
ment, a relation between the value of # and the value of 
the current is obtained. But, as the same current is sent 
through the coil of the standard galvanometer, the ob- 
served deflection of the needle of that instrument gives 
another relation between // and C. From the two equa- 
tions expressing these relations the values of H and C 
can be found. Full details of the construction of Kohl- 
rausch’s apparatus and of the calculation of its constants 
will be found in the paper above referred to. 
In this method it is assumed that the value of # is the 
same at both instruments, an assumption which for rooms 
not specially constructed for magnetic experiments cannot 
safely be made. An instrument which is not liable to 
this objection has been suggested by Sir William Thomson, 
A short account of this instrument and its theory will be 
found in Maxwell’s “‘ Electricity and Magnetism,’ vol. ii. 
p- 328. 
In the application of what has gone before to the 
graduation of galvanometers, we shall have to deal with 
the quantities resistance and potential, and in our calcu- 
lations to measure potentials in volts, resistances in ohms, 
and currents in amperes. A full explanation of the terms 
resistance and potential would require a treatise on elec- 
tricity, but perhaps a very short explanation of what is 
meant bya volt, by an ohm, and by an ampere may not 
be here out of place. 
Two conductors are at different potentials when, on 
their being put in contact, electricity passes from one to 
the other. The difference of potential between them will 
be made manifest if one of them be connected with an 
electrically insulated plate which forms one of the scales 
of a delicate balance, and the other with a second insu- 
lated plate parallel to, and at a very small distance from 
the first plate. If the conductors be at different potentials 
the plates will attract one another, and the force of attrac- 
tion may be weighed by means of the balance. With 
certain arrangements to ensure accuracy, a balance may 
be constructed by means of which the difference of poten- 
tials between two conductors can be measured. Such an 
instrument has been made by Sir William Thomson, and 
called by him an Absolute Electrometer. 
T Continued from p. 1c8 
