RESULTS OF BRITISH TRANSIT EXPEDITIONS. 73 



scientific instruments. But as yet the method is certainly 

 not trustworthy. 



This might be safely concluded from the wide discre- 

 pancy between the new result and the mean of those before 

 obtained. Yet if all the various observations made by the 

 British observing parties agreed closely together, the circum- 

 stance, though it could hardly shake our inference on this 

 point, would yet cause some degree of perplexity, since, of 

 itself, it would seem to imply that the method was trust- 

 worthy. Fortunately we are not thus troubled by conflicting 

 evidence. The indications of the untrustworthy nature of 

 the method, derived from the discordance between the results 

 obtained by it and those before inferred, are not a whit 

 clearer, clear 'and convincing though they are, than are the 

 indications afforded by their discordance inter se. The dis- 

 tance derived from northern and southern observations of the 

 beginning of transit ought of course to be the same as 

 that derived from northern and southern observations of 

 the end of transit. If both sets of observations were exactly 

 correct, the agreement between the results would be exact. 

 The discordance between them could only be wide as a con- 

 sequence of some serious imperfection in this method of ob- 

 serving a transit. But the discordance is very wide. The obser- 

 vations of the beginning of transit by the British parties give a 

 distance of the sun exceeding by rather more than a million 

 miles that deduced from the observations of the end of transit. 



I am well assured that neither Continental nor American 

 astronomers will accept the new estimate of the sun's dis- 

 tance, unless which I venture to predict will not be the 

 case the entire series of transit observations should seem 

 to point to the same value as the most. probable mean. 

 Even then most astronomers will, I believe, think rather 

 that transits of Venus do not afford such satisfactory means 

 of determining the sun's distance as had been supposed. 

 This opinion, it is well known, was held by Leverrier, inso- 

 much that he declined to support with the weight of his 

 influence the proposals for heavy expenditure by France 



