THE DEPOSITS OF THE SEA-BOTTOM. 



while the rest were either pure gray or brownish gray. The appellation of Volcanic Mud I have 

 seen no cause of keeping distinct from the Gray deep-sea clay, as both are quite identical as to their 

 macroscopic qualities, and can only be distinguished by a closer examination of their mineral ingre- 

 dients. On the other hand I have thought proper to keep the name of Transition clay, though in 

 itself it is not very characteristic; Murray classifies the specimens in question as Blue Mud; but as 

 the colour is brown-gray or brown and more light than in the Gray deep-sea clay, I think the Transi- 

 tion clay sufficiently distinguished from the Gray deep-sea clay to form a separate type in the system. 



Concerning the colour of the specimens it has to be remarked that the appellation will of 

 course be to a certain degree dependent on a subjective judgment. I have tried to make it as simple 

 and uniform as possible by only using terms formed by a combination of the single colours, so that 

 for inst. the term brown-gray or gray-brown means a colour midway between what is generally termed 

 pure brown or pure gray, grayish brown means a brown colour with a grayish shade etc. As to 

 the lighter and darker shade it must of course also be a matter of subjective judgment which colour 

 is to be called for inst. gray without any additional remarks of its being light or dark; I have used 

 the following scale: white, grayish white, white-gray, very light gray, light gray and gray, and in the 

 same manner with the dark shades. For completeness I have also noted the colour of the specimen 

 when dry, although it is almost the same as that of the wet specimen, only one or more shades 

 lighter. Further I have added the colour of the residue after the dissolution of the carbonate of lime 

 in hydrochloric acid; the residue of the specimens, which only contain a little lime, is, of course, 

 of the same colour as the specimen itself, while in the specimens with much lime the colour of the 

 residue is considerably darker while the tone of colour itself is unaltered. The colour of the bottom 

 specimens is almost exclusively dependent on the colour of the clay, and this, as has been shown by 

 Schmelck, arises from the different degree of oxidation of the iron; the lighter or darker shade is in 

 proportion to the number of Foraminif era ; that the mineral contents play only a small part, may be 

 seen from the fact that the samples taken near the coasts of Iceland and Greenland do not differ 

 from each other to any appreciable degree with regard to colour, although the sandy ingredients at 

 the coasts of Greenland consist of common light arenaceous quartz, while at Iceland they chiefly 

 consist of brown volcanic substance. 



As to the consistency of the samples I have used the expression sandy-clayey or clayey- 

 sandy, when by rubbing a small quantity between my fingers I could perceive the presence of a great 

 deal of sand, while I have used the appellation clayey, when sand was only to bo perceived to a 

 slight degree, and richly or finely clayey, when sandy ingredients were not felt at all. The appellation 

 plastic could not, in my opinion, be used of any of the samples. Some of the bottom specimens con- 

 sist of completely unsorted material, containing all sizes from small stones to the finest clay, and thus 

 they resemble very much the till. Of organogen ingredients that may have a perceptible influence 

 on the macroscopic quality of the specimen, the spicules are to be mentioned: in most samples of the 

 Globigerina clay they are found in a perceptible quantity, but only in a few to so large a degree as 

 to give the sample a particular entangled consistency; this is the case with no. 45, west of the Faroe 

 Islands, and most particularly with no. 78 southwesth of Iceland, this latter specimen being the one 

 containing the largest quantity of organic ingredients, though it does not, according to its locality, 



