1853. ] OF THE ROYAL INSTITUTION. 237 
relation to magnetism and electricity was inferred from the dual 
nature of these powers, and the necessity in all cases and at all times 
of a relation and dependence between the polarities of the magnet, 
or the positive and negative electrical surfaces. .With respect to 
gravity a more hesitating opinion was expressed, because of the 
difficulty of observing facts having any relation to time, and because 
two gravitating particles or masses did not seem to have any neces- 
sary dependence on each other for the existence or excitement of 
their mutual power*. On the present occasion a passage was 
quoted from Newton which had since been discovered in his works, 
and which, shewing that he was an unhesitating believer in physical 
lines of gravitating force, must from its nature, rank him amongst 
those who sustain the physical nature of the lines of magnetic and 
electrical force: it is as follows, in words written to Bentley : + 
«‘That gravity should be innate, inherent and essential to matter, 
so that one body may act upon another at a distance through a 
vacuum, without the mediation of anything else, by and through 
which their action and force may be conveyed from one to another, 
is to me so great an absurdity, that I believe no man who has in 
philosophical matters a competent faculty of thinking, can ever fall 
into it. Gravity must be caused by an agent acting constantly 
according to certain laws; but whether this agent be material or im- 
material, I have left to the consideration of my readers.” 
Finally, reference was made to Sabine’s remarkable observation, 
sustained as it has been by Wolf, Gautier, and others, of certain coin- 
cidences existing between the appearance of solar spots and the 
diurnal variation of the magnetism of the earth. Scuwase has 
been engaged in carefully observing the spots on the Sun since the 
year 1826. He has found them gradually to increase in number and 
size from year to year, and then decrease ; then again increase, again 
to decrease, and so on in a regular period of about ten years. The 
following is a part of his table { giving the years of the maxima and 
minima of spots : 
Groups in the Days of no Days of 
year. spots. observation. 
1826 
1828 shee Ta ns athe hue ete > 20m 
1833 ee MOOT! cscs eho oy sess! |(s vetace On 
1837 isd 155) Hague: one (Us - + 168 
1843 ee Masel: «i LAD. . ol w (ole Ole 
1848 Feige BhU) erie ate Ora -. 278 
1851 
* Philosophical Magazine, 4th Series, 1852, III. 403. (3246.) 
t+ Newton’s Works, Horsley’s edition, 4to, 1783, Vol. IV. p. 438, or the Third 
Letter to Bentley. 
t Humboldt’s Cosmos, III. 291, 292. Biblioth¢que Universelle, 1852, XX, 184, 
