July 20, 1896.

167

THE AUSTRALIAN PHOTOGRAPHIC JOURNAL.

Mr. James Stirling, of the Geological Department, in a paper read before the Victorian Institute of Surveyors, pointed out the necessity of undertaking topographic surveys, and enumerated, I believe, the advantages that were offered by the application of Photography to that purpose.

Mr. A. C. McDonald, in his Presidential address, Section E ot the Australasian Association for the Advancement of Science, at the Adelaide meeting in 1893, recommended the execution of topographic charts in Australia so urgently demanded by geographical science.

Mr. J. H. Harvey, Mr. E. P. Bishop, Mr. C. H. Harris, and others published valuable and practical papers on the application of Photography to surveying in the reports of the A.A.A.S.

A research committee for promoting this class of work

was appointed at the Hobart meeting of the A.A.A.S. in 1892, consisting of Sir James Hector, Prof. Tate, Mr. F. Belstead, and Mr. E. P. Bishop, with Mr. J. H. Harvey as Secretary, and was re-elected at the Adelaide meeting in 1883, but ceased to be the following year, and since then we have heard nothing more about Phototopography. In consequence of these circumstances, and with the opportunity afforded by the Photographic Congress, it seemed to me that the time had arrived for re opening the subject, in order to remind the engineering and surveying professions, the influential scientific bodies, and the Governments in Australia that Phototopography has grown in importance, with increased resources, and a wider sphere of usefulness, and, therefore, deserves their earnest consideration.

This is the principal motive that induced me to compile these notes.

A TURMERIC PRINTING PROCESS.

7V WRITER in the Photographische Chronik describes ** this as followsTurmeric is derived from the rhizome of two varieties of plants, Curcuma longa and Curcuma, rotunda ; the best kind is the Chinese, the next the Japanese, the worst the Barbadoes. Turmeric may be obtained in the form of powder, and gives up to alcohol its peculiar orange colouring matter, a solution of which on paper or metal gives a negative from a negative as the colour is discharged by light, and only by development with spirit or water, or, with long exposure, by the former alone gives positives.

It can be used for zincography, photo-lithography, and three-colour printing. For zincography it is used as follows;—10 parts of Chinese turmeric should be dissolved in 100 parts of alcohol. If chloroform is used instead of alcohol, more soluble matter is extracted, and with the addition of 5 parts of oil of lavender it withstands acid better, and the solution is more sensitive. In order to judge better of development, 2 parts of a saturated alcoholic solution of methyl-violet should be added. The image thus obtained is quite as resistant as asphalt, if not developed. The development is effected with alcohol. Although this process can be used for zinc etching, it presents no advantages over the albumen or fish-glue processes.

For photogravure it possesses the following advantages : It does away with the costly carbon paper and its concomitant disadvantages of slow drying after sensitising and slow development, the formation of blisters, and the difficulty of seeing the image in the etching bath.

It must not be assumed that there is any difficulty in coating the turmeric solution, or that the asphalt will dissolve. The asphalt grain is rendered insoluble by the heating and by exposure to light.

For photo-lithography, ordinary litho paper is coated wdth the above-mentioned turmeric and lavender solution, dried and exposed. Then the paper is squeegeed to a zinc plate moistened with spirit, or to a stone moistened with water; these are then warmed from below till the resin has melted, and then the paper removed by damping, and the zinc or stone moderately etched. For zinc, the etching solution is composed of

W ater .. .. .. 1000 parts.

Gum solution (1 ; 5) .. ..100 ,,

Nitric acid .. .. .. 15 ,,

for a stone, of

Water ,. ., .. ,. 100 parts.

Gum solution....................... 40 ,,

Acetic acid .................... 10

The stone, when long runs are required, is inked up, and again etched. The advantages of this process are that

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