347 
equations of condition, instead of the methods by which Professor 
Forbes had obtained data for twelve, and Professor Thomson for 
thirty-two equations of condition. The method adopted in the 
present communication, although not susceptible of such minute 
accuracy as the more elaborate methods referred to, seems to be as 
accurate as is necessary for a fair representation of the phenomena, 
and has a great advantage in point of simplicity and ease of working. 
In the present communication the practical methods of calculating 
the amplitudes and arguments of the successive terms in the har- 
monic expression of a periodic variation are fully explained, as it is 
believed the method will be found useful in the reduction of almost 
every class of meteorological observations, and as in this country, at 
all events, there is not much familiarity with it among practical 
meteorologists. 
The following Donations to the Library were announced 
Tierring Fisheries of Scotland. 1860. — From the Board of 
Fisheries. 
Comptes Pendus hebdomadaires des Seances de l’Academie des 
Sciences. No. 16, 
Peport and Diagram showing the Pise and Fall of the Irawadi 
Piver for the Three Years 1856-58= — From the Secretary of 
State for India. 
Total Solar Eclipse, I860, July 18. Pevised Path of the Shadow. 
8vo. — From J. B. Hind, Esq. 
The Atlantis. No. V. January, 1860. 8vo.-=-From the Catholic 
University of Ireland. 
Drawings of the Two Araucarites of Granton Quarry.—” From Bobert 
Allan, Esq. 
