122 P. E. Chase on Terrestrial 
11. The residual errors in the monthly determinations of the 
Horizontal Force and of the Dip ‘are thoroughly confirmatory 
of a semi-annual inequality, having its epochs coincident, or — 
nearly so, with the sun’s passage of the equator ;” p. 803. — 
12. There appears to be “an increase of the Dip and of the 
Total Force, and a deflection of the north end of the Declination — 
magnet teward the West, in both hemispheres, in the months ot — 
October to March, as compared with those from April to Sep — 
tember.. . . The greater proximity of the earth to the sim 
in the December compared with the June Solstice most naturally 
presents itself as a not improbable cause; but we are as yet 100 
little acquainted with the mode of the sun’s action on the mag — 
netism of the earth, to enter more deeply into the question a 
present ;” p. 307. a 
I have neither the leisure nor the ability to undertake an ee 
haustive analysis of the results thus brought together; but I : 
present them as well worthy of a profound mathematical invest — 
gation, as confirmatory in very striking and minute particulars 
of my mechanical hypotheses, and as furnishing new and strong 
ptesumptive evidence of that marvellous simplicity of force 0 
which many independent branches of modern physical research 
have pointed out in the barometer. (Proceedings of the Roy: 
June 16, and of the Am. Phil. Soc., June 17, 1864.) 
Besides the differential or tidal action of the mo 
slight tendency to diminish the weight of the air 
moon, and to increase the weight of that which 1s most Te 
mete. In proportion as this tendency is exerted i | 
with, or in opposition to, that of the sun, the mea 
moon at the commencement of each new month, th 
in the aerial rotation-spheroid produced by lunar 
changes in the average temperature of day and night at ¢! 
ent seasons and different years, &c.), it may yet, perhaps, be 
