BRITISH SCIENTIFIC ASSOCIATION. 465 



some elevated station in the Southern Hemisphere. In. the mean time, and to gain 

 (as it were) a sample of the results -which might be expected from a more syste- 

 matic search, Prof. Piazzi Smyth undertook, last summer, the task of transporting 

 a large collection of instruments — meteorological and magnetical, as well as 

 astronomical — to a high point on the Peak of Teneriffe. His stations were two in 

 number, at the altitudes above the sea of 8,840 and 10,700 feet respectively ; and 

 the astronomical advantages gained, may be inferred from the fact, that the heat 

 radiated from the moon, which has been so often sought for in vain in a lower 

 region, was distinctly perceptible, even at the lower of the two stations. 



" The researches relative to the Figure of the Earth and the Tides are intimately 

 connected with Astronomy, and next claim our attention. The results of the 

 Ordnance Survey of Britain, so far as.they relate to the earth's figure and mean 

 density, have been lately laid before the Royal Society by Col. James, the 

 Superintendent of the Survey. The ellipticity deduced is a ? -g--^3-. The mean 

 specific gravity of the earth, as obtained from the attraction of Arthur's Seat, near 

 Edinburgh, is 5'316; a result which accords satisfactorily with the mean of the 

 results obtained by the torsion balance. Of the accuracy of this important work, 

 it is sufficient to observe, that when the length of each of the measured bases (in 

 Salisbury Plain and on the shores of Lough Foyle) was computed from the other, 

 through the whole series of intermediate triangles, the difference from the 

 measured length was only 5 inches in a length of from 5 to 7 miles. 



" Our knowledge of the laws of the Tides has received an important accession in 

 the results of the tidal observations made around the Irish coasts in 1851, under 

 the direction of the Royal Irish Academy. The discussion of these observations 

 was undertaken by Prof. Haughton, and that portion of it which relates to the 

 diurnal tides has been already completed and published. The most important 

 result of this discussion is the separation of the effects of the sun and moon in the 

 diurnal tide — a problem which was proposed by the Academy as one of the objects 

 to be attained by the contemplated observations, and which has been now for the 

 first time accomplished. From the comparison of these effects Prof. Haughton has 

 drawn some remarkable conclusions relative to the mean depth of the sea in the 

 Atlantic. In the dynamical theory of the tides, the ratio of the solar to the lunar 

 effect depends not only on the masses, distances, and periodic times of the two 

 luminaries, but also on the depth of the sea; and this, accordingly, may be com- 

 puted when the other quantities are known. In this manner Prof. Haughton has 

 deduced from the solar and lunar co-efficients of the diurnal tide, a mean depth of 

 5 - 12 miles — a result which accords in a remarkable manner with that inferred from 

 the ratio of the semi-diurnal co-efficients, as obtained by Laplaoe from the Brest 

 observations. The subject, however, is far from being exhausted. The depth of 

 the sea, deduced from the solar and lunar tidal intervals, and from the age of the 

 lunar diurnal tide, is somewhat more than double of the foregoing; and the consis- 

 tency of the individual results is such as to indicate that their wide difference from 

 the former is not attributable to errors of observation. Prof. Haughton throws 

 out the conjecture that the depth, deduced from the tidal intervals and ages, 

 orresponds to a different part of the ocean from that inferred from the heights. 



"The phenomena of terrestrial magnetism present many close analogies with 

 those of the tides ; and their study has beeu, in a peculiar manner, connected with 

 the labours of this Association. To this body, aud by the hands of its present 

 general secretary, were presented those reports on the distribution of the 



