466 MR J. Y. BUCHANAN, F.R.S., ON THE 



In the Plate, fig. 1 represents a nodule which was found attached to the rim of a 

 • lead pecten shell. It is represented in one and a half times the natural size. 



Figs. 2 and 2a represent, in twice natural size, a nodule entirely filling up a 

 shell. 



Figs. 3, 3a, and 3b represent, in twice natural size, (3) a nodule found attached to a 

 dead pecten shell ; (3a) the under side of the nodule, showing bases of attachment ; and 

 (3b) a view of the shell, showing surfaces of attachment. 



Fig. 4, in one and a half times natural size, shows a remarkable nugget-shaped 

 nodule. 



Fig. 5, in twice natural size, shows a pear-shaped nodule, with stem of attachment. 



Fig. 6, in twice natural size, shows a spherical nodule of the commonest form. 



Figs. 7 and 7a show a nodule split through the middle, and with a semi-detached 

 nucleus. The half of the kernel protrudes in fig. 7, and the corresponding cavity is 

 visible in fig. 7a. 



All these nodules were got on 21st September 1878. 



The nodules taken for analysis are as follows : — M and N (called Nos. 10 and 14 in 

 original notes) were chosen as average specimens. P was a rather softer and Q a rather 

 more stony nodule. K and R are the kernels and rinds respectively of five nodules. 

 These nodules were split, and the kernels and rinds separated as carefully and as com- 

 pletely as possible. Their approximated weights were — 



Kernels, . . . .1*127 grammes. 



Rinds, .... 10-710 „ 



Total, . . 11-837 „ 



S is an average sample taken from a number of nodules pounded up and mixed. 



The analyses of these samples was undertaken at first only to show the state of 

 oxidation of the manganese. In the case of the Loch Fyne nodules, it was carried 

 further, with a view of showing the nature of the other principal constituents. The 

 analyses under the letters X, Y, and Z constitute together a complete analysis, though it 

 was not at first intended to be such, otherwise the whole of the requisite material would 

 have been prepared and extracted at once. These analyses were made in 1879 by Dr 

 George M'Gowan, F.R.S.E., now of Bangor, and were carried out with the greatest care 

 and attention. 



Analytical Method followed for the Determination of the State of Oxidation 



of the Manganese. 



The analysis of these nodules was conducted as follows (any particular point 

 relating to any one nodule will be given in detail along with the analysis of that 

 nodule) : — 



