372 



Ohscrvalions of the late Solar Eclipse. 



These observations were made with an achromatic telescope 

 of 46 inches, on an equatorial stand ; and the measures taken 

 with a micrometer on the vertical diameter ot the sun, on the 

 plane of the equator. These measures being the versed sine's 

 of the sun's seniidiameter 1(3' 13"'5, will give the several angles 

 from the vertex of the sun. 



It was noticed that an error has been published in the Nautical 

 Almanac, of the part of the sun's disc, where the first impression 

 would be made, being 59' from the vertex. The primary con- 

 struction of a solar eclipse being made on the ecliptic, I am of 

 opinion, that it is computed for the vertex of that plane ; which 

 should have been so explained. When vertex is mentioned with- 

 out reference to the plane, we generally suppose it to be the vi- 

 sual vertex on tlie plane of the horizon. The immersion hap- 

 ])ened about half a minute later than computed, and as the 

 moon was decreasing in north latitude the impression would be 

 further from the vertex : on the plane of the ecliptic the angle 

 wa3 64" 55', on the plane of the equator 51° 36', and on the 

 plane of the horizon 20° 37'. 



The undulating stream of light round the disc of the moon 

 should seem to indicate an atmosphere on the surface of that 

 body; and also the disc did not appear to be perfect, but ser- 

 rated; both which circumstances were rendered more observa- 

 ble from the intense light of the sun. 



This eclipse has been total in the northern parts of Russia, on 

 and near the meridian; since the moon's diameter exceeded that 

 of the sun. 



I am, sir, 



Your obedient servant, 

 Blacliheath, Nov. 22, 1816. S. GroombriDGE. 



LXXVII. In- 



