314 E, BKOWN ON THE NATURE OF THE 



about Ij or IJ time as long as broad. These articulations contain 

 a brownish-green granular matter, giving the colour to the whole 

 plant, and again through it to the sea in which it is found so 

 abundantly. The whole Diatom varies in length, from a mere 

 point to 1-lOth of an inch, but appears to be capable of enlarging 

 itself indefinitely longitudinally by giving off further bead-like 

 articulations. Wherever, in those portions of the sea, I threw 

 over the towing net, the muslin in a few minutes was quite 

 brown with the presence of this Alga in its meshes. Again, this 

 summer, I have had occasion to notice the same appearance in 

 similar latitudes on the opposite shores of Davis' Strait where I 

 had principally observed it in 1861. This observation holds true 

 of every portion of discoloured water which I have examined in 

 Davis Strait, Baffin's Bay, and in the Spitzbergen or the Greenland 

 Seas — viz., that wherever the green water occurred the sea 

 abounded in Diatomaceous life, the contrary holding true regarding 

 the ordinary blue water. These swarms of Diatoms do not ap- 

 pear to reach in quantity any very great depth, for in water 

 brought up from 200 fathoms there were few or no Diatoms. 

 They seem also to be affected by physical circumstances, for some- 

 times in places where a few hours previously the water on the 

 surface was swarming with them few or none were to be found, 

 and in a few hours they again rose. But the Diatom I found plays 

 another part in the economy of the Arctic Seas. In June 1861, 

 whilst the iron-shod bows of the steamer I was on board of crashed 

 its way through the breaking-up floes of Baffin's Bay, among 

 the Women's Islands, I observed that the ice thrown up on 

 either side was streaked and discoloured brown ; and on examin- 

 ing this discolouring matter I found that it was almost entirely 

 composed of the siliceous moniliform Diatom I have described as 

 forming the discolouring matter of the iceless parts of the icy sea. 

 I subsequently made the same observation in Melville Bay, and 

 in all other portions of Davis Strait and Baffin's Bay where 

 circumstances admitted of it. During the long winter the Diato- 

 macecB had accumulated under the ice in such abundance that when 

 disturbed by the pioneer prow of the early whalers they appeared 

 like brown slimy bands in the sea, causing them to be mistaken 

 more than once for the waving fronds of Laminaria longicruris (De 

 la Pyl.), which, and not L. saccharina, as usually stated, is the 

 common Tangle of the Arctic Sea. On examining the under surface 

 of the upturned masses of ice, I found the surface honeycombed, and 

 in the base of these cavities vast accumulations of Diatomacece ; 

 leading to the almost inevitable conclusion that a certain amount of 

 heat must be generated by the vast accumulations of these minute 

 organisms, which thus mine the giant floes into cavernous sheets. 

 These are so decayed in many instances as to be easily dashed on 

 either side by the " ice chisels " of the steamers which now form 

 the majority of the Arctic-going vessels, and they get from the 

 seamen, who too frequently mistake cause for effect, the familiar 

 name of " rotten ice." I have since found that in noticing the 

 Diatomaceous character of these slimy masses, I was forestalled 

 by Dr. Sutherland ("Journal of a Voyage," &c., 1852, vol. i., 



