It seems to have been proved that plants and animals may, at certain unknown intervals, “mutate”; and mutation is a fine word to express our recent view of one of the essential factors in evolution. But it is a cloak for an ignorance avowedly less mitigated than when we thought to have found a complete explanation of the causes of evolution in “environment”.
In a sketch such as the present, outlines alone are possible, detail cannot be elaborated. If it has suggested enough of atmosphere to show the vastness of the landscape spreading out before our eyes back into the past and on into the future, the task has been accomplished. There are many detailed volumes which follow out one or other special line of enquiry along the highroads and by-ways of this long traverse in creation. If the bird’s-eye view of the country given in this book entices some to foot it yard by yard under the guidance of specialists for each district, it will have done its part. While to those who will make no intimate acquaintance with so far off a land it presents a short account by a traveller, so that they may know something of the main features and a little of the romance of the fossil world.
APPENDIX I
LIST OF REQUIREMENTS FOR A COLLECTING EXPEDITION
In order to obtain the best possible results from an expedition, it is well to go fossil hunting in a party of two, four, or six persons. Large parties tend to split up into detachments, or to waste time in trying to keep together.
Each individual should have strong suitable clothes, with as many pockets arranged in them as possible. The weight of the stones can thus be distributed over the body, and is not felt so much as if they were all carried in a knapsack. Each collector should also provide himself with—
A satchel or knapsack, preferably of leather or strong canvas, but not of large size, for when the space is limited selection of the specimens is likely to be made carefully.
One or two hammers. If only one is carried, it should be of a fair size with a square head and strong straight edge.
One chisel, entirely of metal, and with a strong straight cutting edge.
Soft paper to wrap up the more delicate fossils, in order to prevent them from scraping each other’s surfaces; and one or two small cardboard boxes for very fragile specimens.
A map of the district (preferably geologically coloured). Localities should be noted in pencil on this, indicating the exact spot of finds. For general work the one-inch survey map suffices, but for detailed work it is necessary to have the six-inch maps of important districts.
A small notebook. Few notes are needed, but those few must be taken on the spot to be reliable.
A pencil or fountain pen, preferably both.
A penknife, which, among other things, will be found useful for working out very delicate fossils.
APPENDIX II
TREATMENT OF SPECIMENS
1. The commonest form in which fossils are collected is that which has been described as impression material (see [p. 12]). In many cases these will need no further attention after the block of stone on which they lie has been chipped into shape.
In chipping a block down to the size required it is best to hold it freely in the left hand, protecting the actual specimen with the palm where possible, and taking the surplus edges away by means of short sharp blows from the hammer, striking so that only small pieces come away with each blow. For delicate specimens it is wise to leave a good margin of the matrix round the specimen, and to do the final clearing with a thin-bladed penknife, taking away small flakes of the stone with delicate taps on the handle of the knife.
Specimens from fine sandstones, shales, and limestones are usually thoroughly hard and resistant, and are then much better if left without treatment; by varnishing and polishing them many amateur collectors spoil their specimens, for a coat of shiny varnish often conceals the details of the fossil itself. Impressions of plants on friable shales, on the other hand, or those which have a tendency to peel off as they dry, will require some treatment. In such cases the best substance to use is a dilute solution of size, in which the specimen should soak for a short period while the liquid is warm (not hot), after which it should be slightly drained and the size allowed to dry in. The congealed substance then holds the plant film on to the rock surface and prevents the rock from crumbling away, while it is almost invisible and does not spoil the plant with any excessive glaze.