98 REPORT—1848. 
To the Assistant-General Secretary. 
Dublin, 27th of July, 1848. 
Dear Sir,—For the last four months I have been so much out of health by 
previous over-exertion of mind and body, that some repose became indispen- 
sable, and I regret to say that I shall be unable, from this cause, to complete 
the Report on the Facts of Earthquakes, entrusted to me by the British As- 
sociation, so as to present it, as [ had hoped and intended, at the ensuing 
Meeting. Much progress has been made with the most laborious parts of it, 
and should health permit, I expect to have the honour of presenting it next 
year, in case the Association deem me worthy of continuing the recommen- 
dation for the Report. 
It is also my duty, as the first named on a Committee for the Construction 
of a Self-Registering Seismometer, to state the progress that has been made :— 
Working drawings of the instrument and of its several parts have been 
prepared and carefully considered, but as the acting members of the Com- 
mittee were unwilling to incur any outlay for actual construction, until per- 
fectly clear in every respect as to the principles and details of the instrument, 
and as some questions arose of considerable mathematical nicety in deter- 
mining, they have not as yet put into hand any part of the work. Professor 
Lloyd, one of the Committee, has kindly promised the reporter to solve those 
questions, when we expect that the instrument will be forthwith completed, 
and a plan determined for its being set to work. We have therefore to ask 
the Association to continue to the same Committee and in the same form the 
‘grant of 50/. made last year for the above purposes. RoperT MALLET. 
Concluding Report on the Gaussian Constants. By ApoLtpHEe ERMAN. 
Tue annexed addition to this year’s Report on the Correction of Gaussian 
constants consists in tables containing primary equations for the 24 unknown, 
viz. the corrections of the constants, resulting from magnetic elements ob- 
served in the Atlantic Ocean, and in some points of the North Sea and of the 
Baltic, and a final table (marked (14), and to be substituted for Table (6) — 
of the first report printed in the volume for 1846), presenting again the 24 
Jinal equations for the 24: corrections in the last and most complete form that 
may be given to these expressions by the whole set of observations that has 
till now come to our disposal. Indeed these equations are the full abstract 
of what can be added to the Gaussian theory of terrestrial magnetism, by 
610 magnetic elements between April 1828 and November 1830 ; and as each 
of the primary equations relating to points between Taheiti and Portsmouth 
reposes upon a due combination of from three to five single observations, 
the number of contributing observations amounts to upwards of 900. A 
simple resolution of these equations will now assign to the corrections Ag**, 
Lea ae (that must be applied to g*°=—108°855, g*'= —152°589..... 
viz. to the numbers previously adopted by M. Gauss), the most probable 
values that can be obtained by the before-said stock of data for 1829, and 
the weight of the same corrections. 
A. ERMAN. 
