Dear Sir,—

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.

Unguja, August 26, 1889.