wash out all traces of sea water as a preliminary. The
specimen must be _repeatedly_ washed by decantation, until the
washings are perfectly free from chlorine, when the whole may be
thrown onto a filter _merely_ to drain. The turbid water which passes
through is allowed to stand so that the suspended matter may settle,
and after decanting the clear supernatant water, the residuum is again
thrown on to the filter.

The washing and getting ready for the drying oven will, in some cases,
require days to carry out, if we wish to avoid losing anything.

So far the proceeding is exactly the same, except draining on a
filter, which would be adopted for preparing for the microscope. On no
account should the opportunity be missed of mounting several slides
permanently for microscopic examination. Drawings or photographic
enlargements will render us independent of direct microscopic appeal,
which is not at all times convenient.

The substance, if drained and allowed to dry on the filter, will
adhere most tenaciously to it, so that it is better to complete the
drying in a porcelain or platinum capsule, either by swilling the
filter with a jet of water or by carefully removing with a spatula.
The most strenuous care must be used not to contaminate the specimen
with loose fibers from the filter.

The perfectly dried matter is best treated in exactly the same way as a
residuum in water analysis. It is a common thing to ignite the residuum,
and to put the loss down, if any, to water. This ought not to satisfy an
accurate observer, since organic matter, carbonates--especially in
presence of silica--will easily add to the loss. The best plan is to
heat a small portion very cautiously, and note if any smell or
alteration in color, due to carbon, etc., is perceptible, and to proceed
accordingly.

I have seen some very satisfactory analyses made on board ship by a
skillful use of the blowpipe, where liquid reagents would be very
inconvenient to employ.

It will be necessary to say a few words as to the way in which
soundings are made at sea. When the bottom consists of sand, mud, or
other loose matter, it is easy enough to bring specimens to the
surface, and, of course, we know in such a case that the bottom has
been reached, but, in the event of the bottom being hard and rocky, it
is not easy to say that our sounding has been successful: and here we
meet with a difficulty which unfortunately is most unsatisfactorily
provided for.