11 



THE TEANSIT OF VENUS 1874. 



With special reference to the importance of determining the 

 true distance of the Sun in connection with Meteorology. 



By F. Abbott, F.R.A.S., F.E.M.S. 



[_Bead 8th A^ril, 1872.] 



The title of the present paper may appear at first sight 

 somewhat paradoxical. It may be asked what has the transit 

 of Venus to do with Meteorology? The answer is — the 

 transit of Venus is the best means of procuring the sun's 

 true distance from the earth, and the sun has everything to 

 do with Meteorology. The relation of these subjects to each 

 other appears an interesting question for discussion. 



The time appears now to have arrived, since such inesti- 

 mable additions as spectrum analysis and photography have 

 been applied to the telescope, for the better examination of 

 celestial objects. When this is accomplished, the physical 

 laws which, by the agency of the sun and planets, influence 

 the Meteorology of the earth cannot fail to be better understood. 



The study of Astronomy requires mathematical knowledge 

 of the highest order, and its truths are not at all times open 

 to ocular demonstration. But on the other hand, the astounding 

 spectacles in Meteorology, storms with thunder, lightning, 

 &c., could not fail strongly to impress the imagination of man, 

 and lead him to conclude that meteorological phenomena bore 

 directly on his well-being. 



But if these two sciences were bom at the same time, they 

 are far from having made the same progress. Astronomy 

 has long ago attained a certainty so great, that it is now con- 

 sidered the first of all sciences of observation. Meteorology, 

 on the contrary, is still in its infancy; it requires the applica- 

 tion of different laws of physics to particular phenomena. 

 Meteorology, therefore, could make no real progress until the 

 physical sciences were sufficiently advanced, the most impor- 

 tant of which for meteorology is electricity, which dates back 

 scarcely a century, and at the present time its operations in 

 nature are but little known ; but in whatever way these phe- 

 nomena offer themselves to the earth, they are analogous with 

 solar physics. 



There is no problem in astronomy which has had so much 

 attention paid to it as that which proposes the true parallax of 

 the sun. Different results have been arrived at by different 

 observers over a long space of time, and yet it remains an open 

 question to be determined at the forthcoming transit in 

 December, 1874. The earth's true distance from those power- 

 ful solar influences, which in many ways affect its atmosphere 

 is a problem much required to be solved. By this means only 



