PUBLIC RECORD OFFICE
Reference :-
C.O. 885
ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO
22 PUBLIC RECORD OFFICE, LONDON
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The impression or counterpart of a fossil should always be pre- served, as it may assist materially in the interpretation of the fossil and even afford evidence of additional features. Sometimes between a fossil and its counterpart there is a narrow space which is in fact a cast of the shell or outer covering of the organism.
Not only should a rock specimen containing a fossil be cure- fully wrapped up, but any part of its surface showing evidence of the organism should be specially protected with cotton wool, moss or similar material. The specimens should be packed in boxes and the interspaces filled up, to prevent shifting, with flexible elastic material, such as crumpled paper, shavings, straw, grass, or in default of these even soft clay or earth, but not fine unyielding material such as sawdust, sand, grain or chaff, which are apt to work out from between and beneath speci- mens. The boxes should be as small as possible, as large boxes suffer more from concussion in transport, but small boxes packed in larger cases travel well.
Friable fossils such as shells in unconsolidated beds are usually best preserved in the matrix. So far as they are exposed to view, they should be slowly dried in the sun or by the careful applica- tion of artificial heat, and then while still warm immersed in a weak solution of gum tragacauth, which gives a less glossy surface than gum arabic. Boues of a similar friable character should be dried in the same manner and then dipped at once for a few moments in a hot weak solution of gelatine or glue, which should be nearly as fluid as water. They should be treated in this way as soon us they are found and if possible before they are moved. A thin solution of shellac in alcohol sometimes gives good results. Fossil leaves in clay are apt to curl up and crumble if dried. They may be preserved by the application of a solution of gum tragacanth or gelatine.
Pyritized fossils are apt to oxidize and decompose with the production of sulphide of iron and sulphuric acid. They should be dried and while still warm dipped in molten paraffin wax. If decomposition has commenced the specimen should first be soaked for some time in water to remove the sulphate of iron and sulphuric acid that have already formed.
Specimens of considerable size, such as vertebrate skeletons. or large ammonites or groups of shells embedded in a matrix only moderately hard, which are liable to fall to pieces, require careful treatment. The specimen should, while still in the rock, he covered entirely with thin paper, which should be pressed as far as possible into every crevice. Plaster of paris is then poured over the surface thus prepared, and allowed to harden in a moderately thick layer. The specimen may then be excavated and transported as a slab. The paper is necessary to prevent the plaster from adhering so closely to the specimen that it cannot be removed. If there are large bones which require hardening, a hot thin solution of gelatine or glue should first be poured over them and adequate time allowed for drying before they are prepared for transport in the manner above described.
Bones which do not require such careful treatment can be best transported swathed in long strips of linen or calico, which are
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afterwards hardened by the application of flour paste, or the strips may be dipped in the paste before they are wound round the
bones.
Small fragile specimens may be held together by dipping in melted paraffin wax.
Too much stress cannot be laid on the importance of packing specimens so closely that there is no possibility of any movement in the box in which they are placed for transportation.
Finally, special precautions should be taken to ensure that the specimens are not injured in passing through the custom house. Arrangements should, if possible, be made that they should be exempted from examination or, if this is not conceded, that they should be carefully handled and that the person who packed them should be present to render assistance.
XII.
CLAY AND SHALE.
Specimens of clay may be placed in paper bags or wrapped in paper and then packed in boxes. Large samples may also be taken for examination, on the first opportunity, for small fossils and minerals. For this purpose the clay is dried and then crumbled up with the hand and placed in a linen or cotton cloth, into which water is continuously poured, while the clay is from time to time turned over. The clay gradually escapes through the interstices of the cloth and any small objects such as fossils, minerals, and rock fragments contained in the clay will be left behind. These should be collected, carefully dried, and folded up in soft paper, which should be labelled and sealed with sealing wax, and then packed with similar samples in a small box. Shale, which is hardened laminated clay, should first be converted into a soft clay-like condition by repeated moistening and drying. Where shale or clay contains plant remains, there are often small seeds present which can be separated by washing in the manner described, and these furnish more trustworthy evidence of the nature of the plants than the leaves and stems,
Pure white clay associated with decomposed grauite probably consists largely of kaolin or china clay. A sample should, there- fore, be taken for commercial purposes. A purified or levigated sample should also be prepared by mixing the clay in a large basin with a much greater amount of water so that the combination is quite fluid. After this has been allowed to stand for u few minutes, three-quarters of it is slowly poured off into another vessel, which is allowed to remain undisturbed till practically all the solid constituents have settled to the bottom. If the material thus obtained feels at all gritty when rubbed between the finger and thumb it should be again submitted to the same treatment. The final product should be carefully dried and packed in a paper bag. About two pounds are required for analysis and a deter mination of the value of the sample for the manufacture of china.