l4 THE OLD RED SANDSTONE. 
sons in the open air has by much the best chance of profiting 
by these. There are formations which yield their organisms 
slowly to the discoverer, and the proofs which establish their 
place in the geological scale more tardily still. I was ac- 
quainted with the Old Red Sandstone of Ross and Cromarty 
for nearly ten years ere | had ascertained that it is richly 
fossiliferous — a discovery which, in exploring this formation 
in those localities, some of our first geologists had failed to 
anticipate. I was acquainted with it for nearly ten years more 
ere I could assign to its fossils their exact place in the scale. 
In the following chapters I shall confine my observations 
chiefly to this system and its organisms. To none of the 
others, perhaps, excepting the Lias of the north of Scotland, 
have I devoted an equal degree of attention; nor is there a 
formation among them which, up to the present time, has re- 
mained so much a terra incognita to the geologist. The 
space on both sides has been carefully explored to its upper 
and lower boundary ; the space between has been suffered to 
remain well nigh a chasm. Should my facts regarding it— 
facts constituting the slow gatherings of years —serve as 
stepping-stones laid across, until such time as geologists of 
greater skill, and more extended research, shall have bridged 
over the gap, I shall have completed half my design. Should 
the working-man be encouraged by my modicum of success 
to improve his opportunities of observation, I shall have ae- 
complished the whole of it. It cannot be too extensively 
known, that nature is vast and knowledge limited; and that 
no individual, however humble in place or acquirement, need 
despair of adding to the general fund. 
