hai 
Proceedings of the British Association. 187 
hope of determining differences of longitude by means of the 
corresponding movements of the magnet at the two stations. 
The changes observed in the observations at present under con- 
sideration, were however far greater in magnitude, and placed 
the phenomenon in a much stronger light. _'The last circumstance 
to which Mr. L. invited attention was, that the curves of horizon- 
tal intensity presented, at remote. stations, a much neater agree- 
ment than those of declination: from which it may be inferred 
that a true knowledge of the nature and laws of the disturbing 
causes will be better attained by the examination of i 
changes, (including, of course, those of the vertical intensity;) 
than those which are dependent ape Ae on the nena of the 
acting forces. 
The President also laid on the table the curves representing 
the changes of magnetic declination, observed at Cambridge, 
Massachusetts, by Mr. W. C. Bond and Prof. J. Lovering, on the 
term-days of May and October, 1840. The corresponding obser- 
vations made at Toronto by Lieut. Riddell, were laid down ina 
curve in connection with the latter. The results exhibited the 
same close agreement in the forms of the curves, and in the 
epochs of the successive maxima and minima as had been already 
noticed in Europe, although, (as before remarked, ) all resemblance 
between this and the European system of changes is nearly ob- 
literated. Cambridge is distant about five hundred miles from 
Toronto: me mean beesagrcaetscee at tive tectane: ee is now 9° 20 
West> = 
Sir D. Sesiwsten dence the Gllesning report on the State of 
the Inquiry into the action of gaseous and other Media on the 
Solar Spectrum. In prosecuting this inquiry, my attention has 
been principally directed to the action of the earth’s atmosphere 
upon the solar spectrum, and I hope to be able to present to the 
next meeting of the Association a map of the bands produced by 
atmospheric absorption. I have also made considerable progress 
in constructing a map of the spectrum containing the numerous 
lines and bands produced by the action of nitrous gas. In sub- 
mitting to examination several other gaseous media, my results. 
have been principally of a negative character; but in my experi- 
ments with solid and fluid media, I have been led to many posi- 
tive and interesting results. In order to obtain additional aecu* 
racy of observation, particularly near the extremities of the spec- 
