14 
DoNKiNj on Marine Diatomacem. 
of feudalism^ when the pursuits of war and rapine left science 
no votaries. 
The natural features of this district are not less varied 
than its historical records are attractive. Here are rude 
precipitous promontories, some of sandstone, others of mas- 
sive basaltic columns, rearing their heads majestically above 
the storm, and bidding bold defiance to the onward sweep of 
the incessant surge, which, in its futile efforts to upheave these 
Cyclopean monsters from their primeval birthplace, is scat- 
tered back in clouds of white and sparkling spray, forming 
a picture sufficiently fascinating even to the most apathetic 
of nature^ s admirers. In such situations as these, flat reef- 
shaped rocks of sandstone, covered with a luxuriant growth 
of the larger Algae, stretch far beneath the waves ; at ebb 
tide these are laid bare for a considerable distance, and abound 
in grallatorial bipeds, and in all that would grace an aqua- 
rium. Beyond these" points again, the eye rests on calm, 
sleepy bays, surrounded by a sandy beach, and by sand hills, 
the creation of the winds, and which the matting sea~reed 
{Psamma arenaria) prevents from being dissipated by the 
same element. Here also are the estuaries and mouths of 
several rivers discharging their waters into the ocean, and 
forming harbours for the extensive prosecution of the coal 
trade. 
That a shore such as I have described should abound in 
diatoms might readily be supposed. The method I pursued 
in procuring these I shall now pass on to describe ; I have 
found it superior to any other for obtaining marine forms. 
Professor Smith states, ^ that " the shallow pools left by the 
retiring tide at the mouths of our larger rivers are the 
favourite habitat of marine species. But such localities I 
have found not to be half so prolific in species as the sands of 
still bays, on the shore, where they are exposed by the reflux 
of the tide, at a distance corresponding with the half -tide mar- 
gin. In these places, where the sands are sloping towards 
the sea, and grooved out into small farrows, filled with salt 
water oozing out from behind, the abundance of diatoms 
aggregated into a living mass, imparts to the surface of the 
sand difPerent hues of chestnut and olive ; the diff'erence of 
colour being due to the nature of the species present. These 
coloured patches, it is interesting to observe, are, during the 
sunshine, studded with numerous minute air-bubbles, un- 
doubtedly given off by the diatoms themselves. 
To separate the diatoms thus detected from the surface 
' Synops./ vol i, Introd., p. i. 
