184 
NATURAL HISTORY. 
6. As we know that the corroding action of the sea is incessant, 
and consequently that all sea coasts have been gradually encroaching 
on the lands, from the very first moment that they became sea coasts; 
as we also know with certainty, that, at the period when this action 
first began, the valleys must all have terminated, as they still do, in 
the exact level of the sea, we have a right to conclude that the time 
cannot be very distant when this corroding action first began. 
7th_If we assume that the general average decay of a coast 
is but one foot per annum, (and it will not be denied that it is consi¬ 
derably more upon a larger proportion of coasts) and if we take so 
short a period, geologically speaking, as only one hundred thousand, 
years, we must suppose that more than eighteen miles have been lost 
from the original mouths of all rivers. 
8th.—Had this been the case, we must have found a waterfall, or 
rapid, at the mouth of every river: and consequently all inland na¬ 
vigation from the sea must have been impossible, except in perfectly 
flat countries. 
9th.—As we rarely find such falls, or rapids, at the mouths of ri¬ 
vers, and as we have reason to know on the contrary, that their origi¬ 
nally inclined planes have neither been materially altered in inclina¬ 
tion, nor shortened in extent, we must conclude, that the loss of land 
on all sea coasts, has, as yet, been but small, and, consequently, that 
the unceasing action of the waves has been but of recent origin. 
10.—As the superficial slopes of all hilly countries lead the eye, 
in a regular line, to the level of the sea, in about one mile, more or 
less, according to the consistency of the shores, we cannot avoid the 
very same conclusion, which we have before attained in a more exact 
manner, in the instance of the chalk : viz. that all our present sea 
coasts have been acted upon by the sea but a very few thousands of 
year , and consequently that all existing dry lands were elevated 
above the level of the ocean, at the same recent period .—Field Nat . 
ARTICLE XIX.—SPOTS ON THE SUN. 
Numerous and fanciful notions have been recently broached 
on this subject, but only one seems to have any degree of physical 
probability, viz. that they are the dark, or at least comparatively dark, 
solid body of the Sun itself, laid bare to our view by those immense 
fluctuations in the luminous regions of its atmosphere, to which it 
appears to be subject. Respecting the manner in which this disclo¬ 
sure takes place, different ideas have been again advocated. Lalande 
