300 Peat Bogs. (July, 
its continuity, and if, after this, the bog were to be covered 
up by newer strata, such vacancies would be filled with 
foreign materials similar to the “‘ troubles” or ‘‘ horses” in 
a coal seam. 
In the mountain bogs of the British islands the prevailing 
timber seems to be deal, and some of the sticks are of lengths 
that the fir rarely attains at the present day in these 
countries. The absence of the remains of the oak in the 
highlands of these islands would seem to suggest that the 
oak could not flourish above a certain altitude, which in 
Ireland seems to have been about the 400 feet contour line. 
This would seem to suggest that prior to the age of the first 
growth of the subaérial peat the lowlands, and the hill-sides 
to a certain height, were covered with oak forest, while 
above that height, the hills grew deal, the deal trees then 
flourishing at much greater altitudes than now, as large 
sticks are sometimes found in bogs at heights of above 1000 
and 1200 feet. 
From the above we may regard it as probable that there 
has been, since the glacial period at least, two ages of the 
most active growth of peat—irst, after the great oak forest 
period, and second, subsequent to the deal forest period. 
‘That a considerable break occurred between them is evident, 
but the cause of itis unknown. ‘There may indeed have been 
a third period, while the now submarine bogs were growing: 
this, however, does not appear probable, for at the present 
day the lowland bogs may grow at any height from high- 
water mark to the 200 or 250 contour line: it is therefore 
possible that the submarine bogs were forming at the same 
time as the lower strata of our present subaérial bogs, al- 
though now found under such different conditions. The 
turf-cutters on the sea shore generally tell you that “the 
turf is of the same depth at high- and low-water mark,” 
but they cannot say if the corkers or roots of the trees stand 
perpendicular. If they are correct it would necessitate that 
seaward the peat has sunk more than at the shore-line. 
On a straight shore-line this might be possible, but on the 
indented coasts of our bays it is highly improbable.* 
In studying bogs, one of the greatest difficulties is to pro- 
cure reliable data by which to be enabled to estimate the 
rate at which they grow. Undrained bogs grow; drained 
* Near the shore-line I have seen the corkers standing perpendicular, but I 
never saw an off-shore hole bottomed, as the incoming tide usually drives 
away the turf-cutters before they can take out all the turf; and I very much 
suspect my informants told me what they considered most probable, and not 
what they actually saw. 
