88 TRANSACTIONS. 
ently of a possible error in computing, the formula would he more or 
less affected 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 through 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 
formula 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 
200,0CO 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. 
Ill. Botanical Notes. By Mr James M‘ANDREW, of 
New-Galloway. 
PREFATORY NoTE.—The following lists of Mosses and 
Hepatice—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, limestone and sandstone mosses could be largely increased. 
My sources of information for the following lists are from plants 
gathered by myself; from specimens sent to me by Mr Charles 
Scott; Dr W. Nichol’s lists of Cryptogams from the Moffat dis- 
