E. Loomis on Solar Spots, Magnetic Declination, ete. 159 
cessive maxima cannot be explained simply by the configura- 
tion of the planets, without also admitting a secular change in 
the magnetism of the sun analogous to the peers change which 
has been observed in the magnetism of the earth. 
Diurnal inequality of the magnetic Declination —In comparing 
the diurnal inequality of the magnetic Declination with the 
amount of spotted surface of the sun, T have taken the obser- 
vations at Prague as the standard, because these observations 
are at least as suitable for this purpose as those of any other ob- 
servatory, and because they are the observations which Profes- 
sor Wolf has chiefly employed in his comparisons. During the 
eighteenth century, sigs aca of the magnetic peep were 
madé at Montmorency, France; at Mannheim, Baden ; ris 
and London. Those of Bea ocees extend from 1777 to “79, 
and were published in the Connaissance des temps for 1780, etc., 
and are copied in the Ziirich Vierteljahrsschrift, v. 5, p. 241; 
those of Mannheim extend from 1781 to 1790, and were pub- 
lished in the Palatine Ephemerides, and are copied j in the Vier- 
teljahrsschrift, v. 6, p. 427; those of Paris were made by Cas- 
sini, and extend from 1784 to ’88, and are copied in the Viertal- 
jahrsschrift v. 2, p. 291; oe those of London extend front 
17 86 to 1805, were made by Gilpin, and were published in the 
London Philosophie eal Transactions for 1806, p. 416. During 
the present century, before the commencement of the Prague 
observations, we have Beaufoy’s observations at London from 
Prague, the mean diurnal change ie the year is obtained oid 
considerably the cae of the mean diurnal change. It is diffi- 
aut to or what correction should be applied to the different 
f observations above enumerated, in order to reduce 
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