88 Transactions. 



ently of a possible error in computing, the formula would lie more or 

 less atfected by any errors which there might be in the assumed values 

 of the masses of the planets, and, as Leverrier has pointed out, the 

 resulting error in the calculated eccentricity of the earth's orbit would 

 increase with the time, so that after several periods the formula could 

 not be trusted. It is also to be noted that his memoir was written in 

 1839, before the discovery of Neptune, and that no account has been 

 taken of the influence of the mass of that planet on the eccentricity of 

 the earth's orbit. Leverrier states that his formula differs completely 

 from those given by Lagrange in 1782, chiefly througli the latter having 

 assumed a mass for Venus, which is nearly half as large again as the 

 value now accepted, and consequently, after a few years, Lagrange's 

 fonnula became inaccurate. Though the uncertainty in the masses of 

 the planets is now much less, caution is necessary in basing conclusions 

 on the values deduced from Leverrier's formula for very remote periods. 

 He has himself limited his computations from his formula to a period of 

 200,()C0 years, viz., 110,000 years before the epoch 1800 and 100,000 

 years after that date, though in a diagram he has given a curve 

 showing the eccentricity of the earth's orbit for 200,000 years after 

 1800. 



I am, Dear Sir, 



Yours faithfully, 



W. H. M. CHRISTIE. 



III. Botanical Notes. By Mr James M'Andrew, of 

 New-Galloway. 



Prefatory Note.— The following- lists of Mosses and 

 Ilepaticse — forming- a contribution to the Cryptogamic Flora of 

 Dumfriesshire and Kirkcudbrightshire — have been compiled from 

 specimens gathered chiefly by myself. They are an expansion of 

 a paper already read on 4th February, 1881, before the Society 

 called " The Bryology of the Glenkens," and recorded in the 

 Transactions of that year. It is more difficult to know the 

 Cryptogamic than the Phanerogamic Flora of a district, and 

 workers in this department of Botany are rare. The Glenkens 

 district is rich in Cryptogams, but the neighbourhood of Moffat 

 and Upper Nithsdale should be equally good and productive if 

 systematically worked. As a general rule that district is the 

 richest which is best searched. The list of lowland, alpine, sub- 

 alpine, Hmestone and sandstone mosses could be largely increased. 

 My sources of information for the following lists are from plants 

 g-athered by myself ; from specimens sent to me by Mr Charles 

 Scott ; Dr W. Nicliol's lists of Cryptogams from the Moffat dis- 





