104 
of the stars, the changes in star clusters and in nebule, together 
with solutions more or less complete of many other questions that 
are now obscure to us. The material which we are now laboriously 
accumulating will then be available in reliable form to unravel the 
knowledge that is now beyond our grasp. 
May I ask you, Mr. President, to accept these photographs for the 
library of the American Philosophical Society, with the best wishes 
of the Royal Astronomical Society of England; and, if you can 
make them available to those who are teaching the science among 
you, so that they may be able to make, say, lantern slides for lecture 
illustrations from them, they are entirely at your service, subject 
only to such restrictions as you and the Council may choose to 
exercise. 
PRESIDENT FRALEY: I accept them on behalf of and with the 
thanks of the American Philosophical Society. 
_ Prof. George F. Barker next read to the Society a paper on 
“ Hlectrical Progress since 1743.” 
Mr. President and Gentlemen :—I take great pleasure in respond- 
ing to the invitation of the Committee of Arrangements to prepare 
for the Sesquicentennial Anniversary of the American Philosophi- 
cal Society a paper upon the development of electrical science since 
1743, with especial reference to the part taken in this development 
by the members of this Society. 
Surrounded as we are to-day with the numberless applications 
which have been made of electricity to the wants of man, it is not 
easy to go back one hundred and fifty years and to realize the 
actual condition of the science of electricity at that early date. It 
is true that Gilbert had already shown, in his remarkable book, De 
Magnete, published in 1600,* that “not only amber and agate 
attract small bodies, but diamond, sapphire, carbuncle, opal, ame- 
thyst, Bristol gem, beryl, crystal, glass, glass of antimony, spar of 
various kinds, sulphur, mastic and sealing wax’’ do so also. He 
had already invented the words, “electricity ’’ and “< electriealeny 
and had differentiated between electric and magnetic forces by 
* De Magnete, Magneticisque Corporibus et de Magno magnete tellwre, Londini, Anno MDC. 
