Nov. 16, 1882} 
NATURE 
67 
_of economic geology cannot be separated from that of the recog- 
_nised principles and methods of inquiry which must be followed 
by the scientific investigator. On the contrary, the more tho- 
roughly we devote ourselves to the prosecution of geology for 
its own sake the better able shall we be to appreciate its 
economic bearings. 
In beginning the duties of this Chair, if I enjoy certain ad- 
vautages over my predecessor, I also at the same time labour 
under considerable disadvantages. The Class Museum formed 
by him, and the other appliances and aids to teaching which he 
laboriously gathered together have been generously handed over 
_to the Chair—and this, I need not say, has greatly smoothed my 
path, But, on the other hand, he has left behind him a reputa- 
tion which must bear hard upon me. He has not only sustained 
but increased the fame of what has been termed the Scottish 
School of Geology, and I feel that it will task all my energies 
to emulate the high standard he maintained as a teacher. It is 
not without diffidence, therefore, that I commence this course ; 
but my hope is that the love of science, which has hitherto 
carried me over many years of a laborious occupation, may at 
least succeed in warming and sustaining the enthusiasm of those 
who come here to study with me what geology has to reveal 
concerning the past and present. 
A METHOD FOR OBSERVING ARTIFICIAL 
TRANSITS* 
AS 
many astronomers who intend to observe the coming 
transit of Venus have neither the time nor means for 
making the necessary arrangements to practice o1 artificial 
transits, the sim le method here proposed may be advanta- 
geously employed. Instead of observing an artificial sun and 
planet placed at a distance of several thousand feet from the 
observer, I would suggest that the real sun be observed, and the 
planet Venus to be represented by a circular disk, held, in the 
common focus of the objec’ive and eye-pieee, by means of a 
narrow metallic arm fastened to the eye-piece. 
The relative motion of the sun and Ve.us can then be pro- 
duced by so adjusting the rate of the driving-clock that the 
angular motion of the telescope on the hour-axis shall exceed the 
diurnal motion of the sun hy seventeen seconds of time per 
hour. In this way, as the atmospheric disturbances of the sun’s 
limb are real, a nearap) roach t) the phenomena observed during 
an actual transit will result. If a light shade glass is employed, 
the opaque disk will be seen before it comes into apparent con- 
tact with the sun. The observer can, however, by an exercise 
of the will, confine his whole attention to the sun’s limb. 
By using a heavier shade-glass the disk will not be seen until it 
is projected against the imageof the sun. The angular diameter 
of Venus at the time of transit being about 65”, the diameter of 
the opaque disk should be 65:/‘sin 1”= 0'00031 77, / being the 
focal length of the telescope used. The position angle of the 
point of contact can be changed at will by simply moving the 
telescope in declination. 
ELECTRIC LIGHTING, THE TRANSMISSION 
OF FORCE BY ELECTRICITY? 
HAVING received the honour of being elected Chairman of 
the Council of the Society of Arts for the ensuing year, 
the duty devolves upon me of opening the coming Session with 
some introductory remarks. Only a few months have elapsed 
since I was called upon to deliver a pre-idential address to the 
British Association at Southampton, and it may be reasonably 
supposed that I then exhausted my stock of accumulated thought 
and observation regarding the present development of science, 
both abstract and applied ; that, in fact, I come before you, to 
use a popular phrase, pretty well pumped dry. And yet so large 
is the field of modern science and industry, that, notwithstanding 
the good opportunity given me at Southampton, I could there do 
only scanty justice to comparatively few of the branches of 
modern progress, and had to curtail, or entirely omit, reference 
to others, upon which I should otherwise have wished to dwell. 
There is this essential difference between the British Association 
and the Society of Arts, that the former can only take an annual 
suryey of the progress of science, and must then confide to indi- 
« By Prof. J. M. Schaeberle, Ann Arbor, Michigan 
Journal of Science. 
2 Address by Dr. C. W. Siemens, F.R.S., Chairman of the Society of 
Arts, November 15. 
From the American 
viduals, or to committee*, specific inquiries, to be reported upon 
to the different sections at subsequent meetings ; whereas the 
Society of Arts, with its 3,450 permanent members, its ninety- 
five associated societies, spread throughout the length and breadth 
of the country, its permanent building, its well-conducted 
Fournal, its almost daily meetings and lectures, extending over 
six months of the year, possesses exceptionally favourable oppor- 
tunities of following up questions of indus'rial progress to the 
point of their practical accomplishment, In glancing back upon 
its history during the 128 years of its existence, we discover that 
tha Society of Arts was the first institution to introduce science 
into the indu trial arts; it was through the Society of Arts and 
its illustrious Past President, the late Prince Consort, that the 
first Universal Exhibition was proposed, and brought to a suc 
cessful issue in 1851 ; and it is due to the same Society, supported 
on all important occa ions by its actual President, the Prince of 
Wales, that so many important changes in our educational and 
industrial institutions have been inaugurated, too numerous to be 
referred to specifically on the present occasion. \ 
Amongst the practical questions that now chiefly occupy public 
attention are those of Electric Lighting, and of the transmission 
of force by electricity. These together form a subject which has 
occupied my attention and that of my brothers for a great num- 
ber of years, and upon which I may consequently be expected to 
dwell on the present occasion, considering that at Southampton 
I could deal only with some purely scientific consilerations in- 
volved in this important subject. I need hardly remind you that 
electric lighting, viewed as a physical experiment, has been 
known to us since the early part of the present century, and that 
many attempts have, from time to time, been made to promote 
its application. Two principal difficulties have stood in the way 
of its practical introduction, viz, the great cost of producing an 
electric current so long as chemical means had to be resorted to, 
and the mechanical difficulty of constructing electric lamps 
capable of sustaining, with steadiness, prolonged effects. The 
dynamo-machine, which enables us to convert mechanical into 
electrical force, purely and simply, has very effectually disposed 
of the former difficulty, inasmuch as a properly conceived and 
well constructed machine of this character converts more than 
ninety per cent. of the mechanical force imparted to it into elec- 
tricity, ninety per cent. again of which may be re-converted into 
mechanical force at a moderate distance. The margin of loss, 
therefore, does not exceed twenty per cent., excluiing purely 
mechanical losses, and this is quite capable of being further 
reduced to some extent by improved modes of construction ; but 
it results from these figures that no great step in advance can be 
looked for in this direction. The dynamo-machine presents the 
great advantage of simplicity over steam or other power-trans- 
mitting engines; it has but one working part, namely, a shaft 
which, revolving in a pair of bearings, carries a coil or coils of 
wire admitting of perfect balancing. Frictional resistance is 
thus reduced to an absolute minimum, and no allowance has to 
be made for loss by condensation, or badly fitting pistons, 
stuffing boxes, or valves, or for the jerking action due to oscll- 
lating weights. The materials composing the machine, namely, 
soft iron and copper wire, undergo no deterioration or change by 
continuous working, and the depreciation of value is therefore a 
minimum, except where currents of exceptionally high potential 
are used, which appear to render the copper wire brittle. 
The essential points to be attended to in the conception of the 
dynamo-machine, are the prevention of induced currrents in the 
iron, and the placing of the wire in such position as to make 
the whole of it effective for the production of outward current. 
These principles, which have been clearly established by the 
labours of comparative few workers in applied science, admit of 
being carried out in an almost infinite variety of constructive 
forms, for each of which may be claimed some real or imaginary 
merits regarding questions of convenience or cost of production. 
For many years after the principles involved in the construc- 
tion of dynamo-machines had been made known, little general 
interest was manifested in their favour, and few were the forms 
of construction offered for public use. The essential features 
involved in the dynamo-machine, the Siemens armature (1856), 
the Pacinotti ring (1861), and the self-exciting principle (1867), 
were published by their authors for the pure scientific interest 
attached to ther, without being made subject matter of letters 
patent, which circumstance appears to have had the contrary 
effect of what might have been expected, in that it has retarded 
the introduction of this class of electrical machine, because no 
person or firm had a sufficient commercial interest to undertake 
