EEPOUT ON THE DEEP-SEA DEPOSITS, 
17 
wet and dried states, and subsequently mounted on microscopic slides for examination 
by transmitted light. As a rule the residue from about 1 gramme of the substance 
was taken for examination, so that the evaluations of the various elements present might 
be comparable in different deposits, but often very large quantities of a deposit were 
taken and the carbonate of lime all removed, in order to have a considerable quantity 
of residue for more thorough examination and study. 
The processes made use of in lithology for isolating mineral species by means of 
strong acids, by the action of electro-magnets, by liquids of high density, by sifting, &c. , 
have all been used by us with varying success, especially when we desffed to get a 
sufficient quantity of a substance for quantitative examination. 
Liquids of high density, such as the compounds of mercury and potassium, and 
borotungstate of cadmium, were useful when dealing with a coarse deposit, but not so in 
dealing with an ordinary deep-sea deposit, where the grains are exceedingly fine, so much 
so, that as a rule it appears to the naked eye as a homogeneous mass. With an ordinary 
magnet and an electro-magnet we were most successful in extracting from a mud or ooze 
all the magnetic particles, such as magnetite, fragments of meteorites, with particles of 
magnetic metals. This was accomplished by placing the magnet, covered with thin 
“ iron ” paper, in a porcelain basin, in which the mud or ooze had been well mixed up 
with water, and moving it slowly about, keeping the magnet as near to the bottom of 
the vessel as possible without touching it ; it was then removed into another basin, 
the paper taken carefully off, and the particles washed into a clean basin to clear 
them from extraneous matter, then re-collected on a slide for examination under the 
microscope. 
The deposit was, after great dilution with clean water, also passed over fixed electro- 
magnets, to collect the magnetic particles, but this was not so convenient in practice as 
the above method with movable electro and permanent magnets. 
The very simple process of fractional decantations, practised often and after a regular 
system, proved to be in the end the most useful and expeditious way of preparing the residue 
for microscopic analysis, and it was this process that we followed in all our examinations. 
In this way we were usually able to separate sufficiently the Residue into the three 
portions noted in the table under the headings: 1. Siliceous Organisms ; 2. Minerals ; 
3. Fine Washings. The decantations were performed with glass or porcelain vessels 
and abundance of water. The whole was kept in motion for some time, and then the 
finer particles were poured off carefully, after continued stirring and shaking. The first 
of these decantations gave us the fine washings, in the second the siliceous organisms 
predominated, while the heavier mineral particles remained behind. Each of these were 
mounted on microscopic slides for further examination. 
The figures in the first column of the tables under Residue give the percentage in 
the whole deposit, and is found by subtracting from 100 the quantity of carbonate of 
(deep-sea deposits chall. exp. — 1890.) 3 
