usually given in descriptive texts. As a reference book, or a text-book, Prof. Kemp's "Hand-book of Rocks" will be found to be a concise, and yet fairly comprehensive treatise, taking up at length a subject which is only outlined here as an aid to geological field work.

CHAPTER XIII

GEOLOGICAL PROSPECTING

Outfit. Lists of the different outfits will be found in the appendix. It is my intention here rather to state general requirements and give some ideas which may serve as a guide in getting together an outfit. The supplies carried in any given case will, of course, depend upon the nature of the country to be prospected, distance from base of supplies, means of transportation, time that the expedition is to be in the field, number of the party, and the natural resources of the country. In general it may be said that everything should be as light and compact as possible. The cooking utensils should be of tin or aluminum and the pots, cups, and plates should fit one within the other so as to take up as little space as possible. Very complete outfits of this kind can be obtained from most dealers in sportsman's supplies.

Canned stuffs are too heavy and bulky for transportation on long trips. The staples-flour, cornmeal, beans, rice, bacon, tea, cocoa and coffee-should be relied upon as much as possible. The condensed and evaporated foods may also be taken. For a complete list refer to the tables mentioned above.

If the members of the party are to pack their own supplies, pack straps should be carefully gone over and adjusted, and an experienced man should be at hand to assist in making up the pack. It is a good plan for men out of training, or new to packing, to accustom themselves to it before actually going on trail, else the consequences may be painful and disastrous to the start, at least, of the expedition.

When pack animals are to be used, the saddles should be thoroughly overhauled; old straps, buckles and loose rivets

should be attended to. Canvas bags are provided to hold the loose articles of the outfit and food should be packed in smaller canvas sacks. The outer bags and the canvas to cover the pack should be waterproof. Canteens and water bags must be taken in dry countries. It should be seen that the packers are provided with horse shoes and nails, extra rope, straps, and buckles, harness awl, and rivets. Nothing is so annoying as to have to stop on the trail to make repairs when there is nothing on hand to repair with. The Mexican freighters especially are likely to go into the field poorly equipped and trust to ingenuity, luck, baling wire and string, to come out all right. They are also likely to appropriate any extra supplies furnished them. It is important that the animals should be kept in good condition, free from saddle galls, and sound at the feet.

It is equally necessary that the members of the party keep their feet in good condition. They should be well provided with foot gear and on a long trip a man who knows something about shoe repairing should be attached to the party. At any rate, a shoemaker's iron last should be carried for the discouragement of nails in the wrong places; awl, heavy needles, and waxed thread will pay many times for the trouble of carrying them. Hob nails, or wood screws used as such, should be replaced as soon as they are lost.

As to clothes, it is not possible to lay down strict requirements; they should be suited to the climate, heavy kahki and corduroy are most serviceable, but the latter is not adapted to use in warm countries. At least one change of shirts and under clothing should be carried when circumstances permit; several pairs of heavy socks should be taken and woolen socks may be worn even in the warmer countries. In the mountains it is well to wear heavier under clothing, preferably woolen, even in the warmer weather, especially when it is cold in the shade or after sun down.

Sleeping bags are convenient in cold weather but are bulky. It is better to carry several light blankets than a single heavy one, and the rubber blanket or poncho is a very good thing

to have. With people who are unaccustomed to sleeping in the open, the tendency is usually to carry too much bedding.

In one's personal kit should be included the necessary toilet articles in such shape as to take up as little room as possible, also needles, thread, and cloth for patching. There should be at least one medicine case in the party, including the simpler remedies, adhesive plaster and tape, absorbent cotton, and a roll or two of bandages.

Unless an expedition is organized on a large scale, every man must be his own doctor and should go into the field in good shape physically. The chances are that as long as he takes proper care of himself he will stay in good shape, barring accidents, such as broken bones. In such work it is necessary that a man should take all proper precautions to stay fit or he will impair his own efficiency and put an added burden upon the other members of the party. It is, of course, desirable that in such a party one man should have a knowledge of medicine and surgery, or at least be familiar with "first aid" methods.

Maps, Instruments and Methods. In starting into a new country it is always desirable to have the best maps obtainable of the district to be covered. The government land surveys or geological surveys publish maps in the United States and Canada; and in many of the Mexican mining districts maps of more or less accuracy may be obtainable. Where no maps are available it becomes necessary to work them up by reconnoissance methods as the work progresses. Map making is out of the field of ordinary geological work, but the geologist should familiarize himself with the methods employed.

If a large area is to be covered, it may be necessary to determine latitude and longitude, so that a chronometer will be carried for accurate time, and a small transit will be used for solar or stellar observations. The sextant is more convenient to carry, but is not so accurate, while the transit has the additional advantage of use in ordinary surveying. An aneroid barometer is useful in determining approximate elevations as the march progresses and in finding local differences of elevation

with considerable accuracy. Field glasses, range finders, and a pedometer or passometer, are valuable adjuncts in sketch mapping.

The large plane table is useful in mapping in open country, and triangulation may be carried out extensively by means of it. A convenient form of alidade is illustrated in Fig. 3. The small plane table may be used for less accurate work and local sketch mapping.

The army sketching case is a drawing board of small size, provided with rollers for carrying a long strip of paper. Upon the board are a compass and sighting device, also a movable protractor for plotting sight lines and distances. This makes a most convenient board for sketch work when traveling upon roads or trail or simply running a traverse line. Distances may be estimated or measured with the pedometer or passometer, or some range finding device, while elevations may be taken by barometer or measurements of slope angles in connection with distances estimated or measured.

Triangulation from a base of known length is a quick and accurate means of measuring distances and locating new points. If the locations of several prominent points of an area have been determined, the re-section method of plane table location (see page 4) is very convenient for locating new points. For rougher sketch mapping in open country, the following method may be used.

A base line is measured roughly by stadia, tape, or pacing, and is laid out upon the plane table sheet. From both ends of this line prominent points are sighted and located by intersections upon the map. Such points may then be occupied and new locations made, gradually extending the field of the map as longer bases or triangle sides are available. In the arid country of the Southwest, which is characterized by ranges separated by wide stretches of plains, where the observer can see for long distances, such triangulation may be carried out easily and quickly and will give fairly satisfactory results. Locations made by sighting the peaks of the opposite range will be much