Tank development is best for the field.  The tanks provided for developing by the Kodak Company are best for fixing also.  A nest of tanks would be a convenience; one tank should be kept separate for the fixing-bath.  As suggested in the Kodak circular, for tropical development a large-size tank can be used for holding the freezing mixture of hypo.  This same tank would become the fixing tank after development.  In the rainy season it is a difficult matter to dry films.  Development in the field, with washing water at 80 degrees F., is a patience-trying operation.  It has occurred to me that a small air-pump with a supply of chloride of calcium in small tubes might solve the problem of preserving films in the tropics.  The air-pump and supply of chloride of calcium would not be as heavy or bulky as the tanks and powders needed for development.  By means of the air-pump the films could be sealed in tin tubes free from moisture and kept thus until arrival at home or at a city where the air was fairly dry and cold water for washing could be had.

While I cordially agree with most of the views expressed by Mr. Fiala, there are some as to which I disagree; for instance, we came very strongly to the conclusion, in descending the Duvida, where bulk was of great consequence, that the films should be in rolls of ten or twelve exposures.  I doubt whether the four-barrel gun would be practical; but this is a matter of personal taste.

APPENDIX C.

My Letter of May 1 to General Lauro Muller

The first report on the expedition, made by me immediately after my arrival at Manaos, and published in Rio Janeiro upon its receipt, is as follows: 

May1st, 1914.

To his excellency the minister of
foreign affairs,
Rio-de-Janeiro. 
My dear general Lauro Muller: 

I wish first to express my profound acknowledgments to you personally and to the other members of the Brazilian Government whose generous courtesy alone rendered possible the Expedicao Scientifica Roosevelt- Rondon.  I wish also to express my high admiration and regard for Colonel Rondon and his associates who have been my colleagues in this work of exploration.  In the third place I wish to point out that what we have just done was rendered possible only by the hard and perilous labor of the Brazilian Telegraphic Commission in the unexplored western wilderness of Matto Grosso during the last seven years.  We have had a hard and somewhat dangerous but very successful trip.  No less than six weeks were spent in slowly and with peril and exhausting labor forcing our way down through what seemed a literally endless succession of rapids and cataracts.  For forty-eight days we saw no human being.  In passing these rapids we lost five of the seven canoes with which