PUBLIC RECORD OFFICE
Reference :-
PPT CO. 885
22 PUBLIC RECORD OFFICE, LONDON
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TQ
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below the surface as circumstances permit, since they are usually depreciated by atmospheric action. In the case of metallic ores every endeavour should be made to reach the point where the sulphide ores," which possess a metallic lustre, commence, but it must be remembered that the sulphide ores are often richer in metal near their upper limit than at greater depths.
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Small specimens of economic mineral products are of com- paratively little use. Seven pounds weight at least of ore or coal should be obtained. It should represent an average sample of material that could be obtained in commercial quantities.
It may be laid down as a general rule that if rocks or minerals are unusually heavy that is, have a specific gravity of over 34, specimens of them should as a matter of course be taken, for they may prove of value for their metallic contents.
Rocks collected with a view to determine their suitability for building purposes should be accompanied by samples of the weathered surface, so as to show the effect of the atmosphere upon them. If a specimen of limestone be taken, it is often useful to obtain also samples of shale, clay,, or river-mud in the same neighbourhood, so that it can be ascertained in what proportions they should be mixed with the lime from the limestone to form a good cement.
Specimens of soil are frequently required for determining the agricultural capabilities of a district. For this purpose 3 or 4 lbs. are required in each case. A sample of soil should be usually accompanied by a similar specimen of the subsoil as well as of the solid rock below, if it is accessible.
Samples should also be obtained of mineral products used by the natives of a district, whether such products are procured locally or from a distance. Specimens illustrating the native methods of smelting or otherwise dealing with minerals are also of importance.
VIII.
BREAKING OFF SPECIMENS.
A geological hammer should be employed for taking specimens of hard rocks. The head should be of tough steel, not too highly tempered, and weigh from one to one and a half pounds. A heavier hammer weighing three or four pounds is useful in the case of really tough rocks, and arrangements should be made to have it at hand when needed. The head of a geological hammer should be square in shape at the front or striking end, and it should be prolonged at the back to a chisel edge which should be at right angles to the handle. The hole for the handle should not be too small, or it will not take a wooden handle sufficiently thick to stand the work. The handle should not be allowed to get too dry, otherwise it contracts and works loose and at the same time the wood becomes brittle. Sometimes the end of the handle which fits in the head is enclosed in a steel sheath. In this case the head is first placed on the other end, and then pushed up to its final position over the steel sheath, which is so constructed that the head can not move further in the same direction and
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fly off, as is frequently the case when an ordinary handle is used. This type of handle lasts longer as it is protected at the point of greatest strain.
In striking off a fragment the hammer is held loosely while it is being swung und when the blow is delivered. The effect of the concussion is therefore due to the momentum of the head, not to force directly exercised by the arm. The rock should be struck obliquely by one of the rectangular edges of the front of the hammer.
It is usual to trim a sample so as to measure about 44" x 3" x 1. For this purpose a small hammer, the head of which weighs about four ounces, is employed. Portions of the weathered sur- face, or of the walls of joints or fissures, should be removed. It is important to avoid giving a battered appearance to the specimen, and the shape should be obtained by striking off splinters and not by hammering down projections.
The production of specimens satisfying these conditions requires considerable practice and takes up a great deal of time. Indeed in some rocks the tendency to split in unforeseen directions is so great as to render success very difficult. For most purposes it is quite sufficient to obtain a fragment of convenient size, and confine the trimming to the removal of awkwardly projecting angles.
Besides the hammer or hammers, two or three cold steel chisels 4 or 5 inches long are useful for getting out minerals and fossils.
IX.
WRAPPING UP AND PACKING.
It is of the greatest importance that specimens should be properly protected from injury and that each should carry with it unequivocal evidence of the locality where it was collected. In most cases it is sufficient to wrap specimens in strong paper. Newspaper, doubled if necessary, will suffice, unless it is too flimsy.
It is convenient to allot a number or letter to each specimen. If letters are employed they should be taken in alphabetical order, recommencing with A after Z has been reached and not at the beginning of each day. The numbers or letters constitute a record of the order in which the specimens were collected. Each specimen should be accompanied by the distinguishing number or letter and the locality and date. A few words of description may also be added. These particulars may be written in a corner of the wrapping paper. After this corner has been folded several times to preserve the writing from injury the specimen is wrapped up with the folded corner next to it and secured with string. The same details should then be written again on the outside. The writing should be in ink, preferably Indian ink, but in cases of necessity pencil may be used, provided the strokes are firm and dark.
As an additional precaution the distinguishing number or letter, and if possible the date, may be scratched or marked on the specimen itself. If fossils, or ancient ripplemarks or similar
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