150 Professor Secchi on the 



calculations connected with the triangulation are rapidly ad- 

 vancing towards their completion." 



In the meantime, the great arc of Eastern Europe has been 

 advancing with unexampled rapidity, and to an extent hitherto 

 unparalleled. Originating in topographical surveys inEsthonia 

 and Livonia, and commenced in 1816, the operations, both 

 geodesical and astronomical, have been completed between 

 Izmail on the Danube and Fugleness in Finnmarken, an ex- 

 tent of 25^- meridional degrees. Next to this in extent is 

 the Indian arc of 21° 21' between Cape Comorin and Kaliana ; 

 and the third is the French arc already referred to, of 12° 22'. 

 It appears by a note presented to the Imperial Academy of 

 Sciences at St Petersburg by M. Struve, that a provisional 

 calculation has been made of a large part of the great arc of 

 Eastern Europe, and that it has been found to indicate for 

 the figure of the earth a greater compression than that de- 

 rived by Bessel in 1837 and 1841, from all the arcs then at 

 his command, — Bessel's compression having also been greater 

 than Laplace's previous deduction. It is naturally with great 

 pleasure that I perceive that the figure of the earth derived by 

 means of the measurement of arcs of the meridian, approxi- 

 mates more and more nearly, as the arcs are extended in 

 dimension, to the compression which I published in 1825 as 

 the result of a series of Pendulum Experiments, which, by 

 the means placed by Government at my disposal, I was en- 

 abled to make from the equator to within ten degrees of the 

 pole, thus giving to that method its greatest practicable ex- 

 tension. — Address to the British Association at Belfast. 



On the Distribution of Heat at the Surface of the Sun. 

 By Professor Secchi. 



1. The heat of the solar image is at the centre almost 

 twice as great as at the borders. This is found to be true, 

 examining the diameters both in right ascension and decli- 

 nation. 2. The maximum of temperature did not appear to 

 be at the centre, but above it, in a point distant from it about 

 3' of geocentric declination. Constructing graphically the 



