For the determination of latitude and longitude there is nothing better than a small four or five inch theodolite not over fifteen pounds in weight.  It should have a good prism eyepiece with an angle tube attached so it would not be necessary to break one’s neck in reading high altitudes.  For days we travelled in the direction the sun was going, with altitudes varying from 88 deg. to 90 deg..  Because of these high altitudes of the sun the sextant with artificial horizon could not be used unless one depended upon star observations altogether, an uncertain dependence because of the many cloudy nights.

Barometers—­The Goldsmith form of direct-reading aneroid is the most accurate portable instrument and, of course, should be compared with a standard mercurial at the last weather-bureau station.

Thermometers—­A swing thermometer, with wet and dry bulbs for determination of the amount of moisture in the air, and the maximum and minimum thermometer of the signal-service or weather-bureau type should be provided, with a case to protect them from injury.

A tape measure with metric scale of measurements on one side and feet and inches on the other is most important.  Two small, light waterproof cases could be constructed and packed with scientific instruments, data, and spare clothing and yet not exceed the weight limit of flotation.  In transit by pack-train these two cases would form but one mule load.

Photographic—­From the experience gained in several fields of exploration it seems to me that the voyager should limit himself to one small-sized camera, which he can always have with him, and then carry a duplicate of it, soldered in tin, in the baggage.  The duplicate need not be equipped with as expensive a lens and shutter as the camera carried for work; 31/4 x 41/4 is a good size.  Nothing larger than 3 1/4 x 5 1/2 is advised.  We carried the 3A special Kodak and found it a light, strong, and effective instrument.  It seems to me that the ideal form of instrument would be one with a front board large enough to contain an adapter fitted for three lenses.  For the 3 1/4 x 4 1/4: 

One lens                                 4 or 4 1/2 focus
One lens                                 6 or 7 focus
One lens telephoto or telecentric        9 to 12 focus

The camera should be made of metal and fitted with focal-plane shutter and direct view-finder.

A sole leather case with shoulder-strap should contain the camera and lenses, with an extra roll of films, all within instant reach, so that a lens could be changed without any loss of time.

Plates, of course, are the best, but their weight and frailty, with difficulty of handling, rule them out of the question.  The roll film is the best, as the film pack sticks together and the stubs pull off in the moist, hot climate.  The films should be purchased in rolls of six exposures, each roll in a tin, the cover sealed with surgical tape.  Twelve of these tubes should be soldered in a tin box.  In places where the air is charged with moisture a roll of films should not be left in a camera over twenty-four hours.