You will remember calling here in last July, just before I took my
holiday.
You left with me for examination a series of rock specimens and some
sediment of lake water from East Africa.
Of the rock specimens, at least six give indications of great interest.
Those two labelled "Iraku I" and "Iraku II" are so rich in gold that
their importance must have been apparent to yourself--unless you mistook
the gold for iron pyrites, an inverse of the customary deception, which
is generally the other way about. The specimen labelled "Marasha" is
simply coal--rather shaley coal, probably a surface fragment. There are
two specimens, unfortunately with their labels missing or
indecipherable, which are a hard bluish green serpentine rock, obviously
related to the "blue ground" of South Africa and probably
diamondiferous. A fifth specimen yields evidence of wolframite, and in
three other samples there is much mica. The lake sediment is being
further examined by a colleague of mine. He believes it to be an
indication of the formation of phosphates in the lake bed or shores
which should be of great importance to agriculture as a constituent of
chemical manure. These phosphates might be derived from birds' dung in
great quantities, from guano in fact.
I assume you have duly registered the exact geographical localities of
these specimens? Otherwise, they are very tantalizing, for they
evidently indicate--if they come from one region and not from a wide
area of travel--one of the wealthiest of African territories.
Pursuant to your wish, however, I shall treat the matter as
confidential. But if you can at any time supply me with the exact
geographical information I require I shall be pleased to write a report
on the collection for the Petrographical Society or for the confidential
information of the Government: whichever you prefer.
Yours faithfully,
DANIEL RUTTER.
Unguja,
_August_ 26, 1889.