77 
1883 .] Sun-spottery. 
light obtained with gas. Mr. W. Crookes, F.R.S., has already 
laid before the public the comparative cost of gas and of the 
eleCtric light (incandescence) as applied in his house, the 
advantage being in favour of the eledtric light, though pro- 
duced under disadvantageous circumstances ; that is to say, 
the motive power had to be produced solely for the purpose 
with a “ silent gas-engine,”— certainly not the most econo- 
mical method of obtaining mechanical power, though the 
only one available in such a locality. 
In an experiment in street-lighting carried out by the firm 
of Siemens and Halske, the eminent electrical engineers of 
Berlin, the cost of lighting up a given area at an equal 
intensity with the eledtric light was found about half that 
of gas. . 
As here also the motive power was not obtained in the 
most economical manner, there can be no doubt that the 
general introduction of the eledtric light will represent a 
considerable saving in money, over and above its other 
advantages. 
IV. SUN-SPOTTERY. 
IN MEMORIAM OF THE LATE PROFESSOR STANLEY JEVONS. 
By A. H. Swinton. 
^QERHAPS in no way has Science exerted a more bene- 
JK ficial influence on society than by the innovations it 
^ has made during the nineteenth century on the old 
astrological notions of our ancestors. As far back as the 
seventeenth century the discovery of the revolution of the 
globe showed that their ideas of aberrant planetary motions 
were mere optical illusions,* and paved the way to a recog- 
nition of the sun as the true centre of the universe. It was 
but a step then to attribute changes in terrestrial phenomena 
to corresponding changes transpiring in its light-giving 
* The question whether the position of the planets is in relation to the sun- 
spots has been discussed by Dr. Muirhead (Phil. Soc. Glasgow, vols, for 1875, 
1880) and Mr. F. B. Edwards (Nature for 1882, p. 293). 
