subject on which I will venture to speak—good sections, sometimes of mote than legal interest, such as the junctions between formations, are often lost to science for want of the necessary funds to have them photographed while they are fresh, or before they become grass-grown. When original observations are made, and perhaps local discoveries—which, of course, can scarcely be hoped to happen at very short intervals—the results are communicated to the local scientific society, and beyond a necessarily brief newspaper notice they seldom find their way into print, and are soon beyond the reach of reference. Geology, above all subjects, hag to depend so much on artificial openings being made in the reeks hat vigilant observers, who will be ready at all times, and often at no little personal inconvenience, to take advantage of any artificial exposures that may he wade, are needed in every district. Of course very much of the value of such scientific work as is proposed depends on its thoroughness. Mere flimsy, or "kid glove," observers, who seem to imagine that the more ground they can contrive to cover, no mutter how imperfectly, the greater their achievements, should be as far as possible avoided.—J. S.
Gleanings.
A Sturgeon, 8ft. long and 230lbs. in weight, was recently caught in the Estuary of the Severn. This magnificent specimen has been purchased by Mr. Montagu Browne, Naturalist, Birmingham. We understand he purposes mounting it and presenting it to the Birmingham Aquarium.
Geological.—Readers of Mr. J. Shipman's paper in the "Midland Naturalist" for January and February last, entitled "Some new Features in the Geology of East Nottingham," in which several important errors in the geological map of the survey were pointed out, will, we feel sure, be glad to learn that Mr. Aveline, the district surveyor of the geological survey, has very recently gone over the ground examined by Mr. Shipman, and will shortly issue a corrected map and memoir of this district.
The Colouring Matter in the Plumage of Birds,—Mr. H. C. Sorby, F.R.S., recently delivered a lecture on this subject before the Selby Naturalists' Society. He commenced by explaining the cause of colour in general, stating it to be due to the absorption of some of the prismatic colours and the reflection of others. White is produced when all the colours are reflected and nene absorbed, whilst black is the result when all are absorbed and none reflected. The colours of feathers are due, first, ta the presence of a colouring matter called pigment, which may be extracted and used as a paint; second, to the reflection of the prismatic colours of light by the peculiar construction of the laminæ in the structure of the feathers. Feathers of the first kind are those which show the same colour both by reflected and by transmitted light. The lecturer exhibited a number of water-colour drawings, painted with the pigments extracted from feathers, and observed that in one instance copper was found to be one of the elements in the composition of the colour, Which is, perhaps, the only case known in the animal kingdom where copper forms part of the normal structure. A connection had been observed between birds having bright coloured plumage and the flowers on planta on which they feed, the colour of the flowers apparently being developed in the feathers of the birds, especially in the yellow colour, whilst birds of prey were usually devoid of yellow colouring. Grey was shown to be diluted black pigment. The second kind of colours are those which, like the iridescence of a soap bubble are caused by the reflection of light from two surfaces nearly parallel; examples of this kind are found in the feathers of the peacock. pheasant, humming bird, &c., the colours not being caused by pigment, but due to a curious optical phenomenon.
