Shoe maker's iron last, awl, waxed thread, sole leather, nails, and knife. (Shoemaker's outfit need not be carried unless the trip is a long one.)

The ration list given above is intended only as a guide in purchasing supplies, and may be varied to suit individual requirements. If travelling in Mexico with Mexican freighters or miners in the party the bean ration should be increased at the expense of rice or corn meal. It is well, if possible, to hire the natives with the understanding that they furnish their own food. In a hot dry country the salt and sugar ration should be cut to a minimum, especially if water is scarce.

The compressed or condensed foods, such as dried potatoes, dried eggs, Erbswurst, pemmican, and soup tablets are useful when it is desirable to cut down the weight, but they cannot be obtained at the smaller towns which are usually the outfitting points for field expeditions.

Ordinary canned stuff should not be carried where it is to be packed any distance, for it is weighty and awkward to handle.

MEASUREMENT OF GOLD AND SILVER BEADS BY MEANS OF THE MICROSCOPE Reference: "The Detection and Estimation of Small Quantities of Gold and Silver." By Luther Wagoner, in Transactions American Institute Mining Engineers, Vol. XXXI, (1901), pages 798 to 810.

The instrument used has an eyepiece with micrometer scale. With the power of 40 diameters, one division is 0.02873 mm.; with 60 diameters one division is 0.02001 mm., which is the power ordinarily used. A clip made

of a small watch spring is used to hold the bead, the jaws of the clip should be polished so as to reflect the bead, giving sharp lines for measurement.

The measurements taken are diameter of the bead, diameter of its base, and the height. An approximation to the volume may be obtained by regarding the bead as a portion of a sphere, but the author deduces a formula taking into account the variation from true spherical form, which is as follows:

Weight =D3×0.00007598 for gold (log-5.8807)

and

D3X0.00004233 for silver (log-5.6246).

D=number of scale divisions of 0.02001 mm. each

The reader is referred to this paper for a description of the methods of manipulating small beads and assaying for small quantities of the metals.

GUIDE TO THE "SIGHT RECOGNITION" OF ONE HUNDRED AND TWENTY COMMON OR IMPORTANT MINERALS1

By A. J. MOSES

The one hundred and twenty minerals are classified by simple easily used field tests involving only color, streak and approximate hardness as shown by Key page 208.

In each division the minerals are in order of hardness and with the description of each is given the composition and Specific Gravity, and a carefully prepared paragraph in fine type as to occurrence and usual associates.

For confirmation fifty simple tests are described on pages 257 to 265 and the tests appropriate to each species are indicated by numbers after the description of the species.

1Copyright, 1912, by A. J. Moses.

207

KEY

A. Minerals as Hard or Harder than Quartz.

In order of hardness 7 to 10, pp. 209 to 212.

B. Minerals Softer than Quartz and Colored both in Mass and in Fine Powder (Streak).

1. Both the Mineral and its Streak are Black or nearly black, p. 213.

2. The Streak is Black, the Mineral is not Black, p. 216. 3. The Streak is Lead-gray or Silver-white, p. 218.

4. The Streak is Yellow to Yellowish-brown, p. 219.

5. The Streak is Red to Reddish-brown, p. 222.

6. The Streak is Green to Blue, p. 224.

C. Minerals Softer than Quartz and Distinctly Colored in Mass

but White in Fine Powder.

1. The Mineral is Violet, purple or blue, p. 226.

2. The Mineral is Green, p. 228.

3. The Mineral is Yellow or brown, p. 233.

4. The Mineral is Red, p. 239.

5. The Mineral is Black, or nearly so, p. 243.

D. Minerals Softer than Quartz, White or Light Gray in Mass and White in Fine Powder.

1. Will not scratch calcite, p. 246.

2. Will scratch calcite but not fluorite, p. 249.

3. Will scratch fluorite, p. 252.