June 30, 1898] 



NATURE 



205 



ence being that the film of chromated gelatine, hardened 

 by the action of light, which forms a resist to the etching 

 fluid, is transferred to the metal plate after being exposed ; 

 a proceeding which aflfords one very important advantage. 

 The gelatine, which remains soluble or unaffected by light, 

 can under these circumstances be washed away by warm 

 water, leaving on the metal plate a resist of graduated 

 thickness. The frontispiece of " The Process Year-Book " 

 for last year is a very fine example of photogravure by 

 the Talbot-Klic process, the work of Mr. Horace Wilmer ; 

 a specimen interesting as showing that, in process work, 

 the amateur may stand fully level with the professional. 

 The frontispiece of the current issue (1898) is a 

 good specimen of similar work by Dr. E. Albert of 

 Munich. 



Printing by hand from the intaglio plate is a very slow 

 process, especially in the case of the finer class of work ; 

 and although we gather from " The Process Year-Book " 

 that very much progress has recently been made in the 

 rapid printing of intaglio plates by machine, the chief or 

 general aim of the process-worker now-a-days is the 

 rapid production of plates or blocks which can be set 

 up with a forme of type, and printed together with the 

 type and without any complication of the method of 

 pnnting. 



Methods of making such photo-typographic blocks 

 are very numerous, but according to that system of 

 working which is now most general, the first and most 

 delicate task is to obtain a negative in which the degrees 

 of transparency are rendered by the increasing size of 

 minute windows ranged in regular order all over the sub- 

 ject ; but where the negative is most opaque the size of 

 each of these windows may be reduced to «//, and where 

 the negative is most transparent the windows may run 

 into each other and give an area of virtually clear glass. 

 Such a negative is obtained if a glass plate or screen, 

 closely ruled with opaque cross-lines, is set in the camera 

 a little way in front of the sensitive plate, each window 

 in the screen forming a pin-hole image of the aperture 

 of the lens. The question of the best use of the ruled 

 screen and the most suitable kind of ruling is a very 

 complex one, as evidenced by several very recondite 

 articles in " The Process Year-Book." The screen-negative 

 having been obtained, an impression is made on a metal 

 plate coated with a sensitive resist, which sensitive resist 

 may be bitumen, sensitive albumen, or, more often in 

 prac'.ice, the highly soluble and almost gum-like gelatine 

 sold as fish glue. Each window of the screen negative 

 makes an insoluble spot of corresponding size on the 

 sensitive film, after which the soluble portions of the film 

 are dissolved away, and the insoluble spots of graduated 

 size form the resist in the next stage : etching the plate. 

 When sufficiently etched, the plate is ready for being 

 printed from, and it naturally gives an impression in which 

 each window of the screen-negative is rendered by a dot 

 of printing ink of corresponding size. 



There are many other methods of photographic process 

 reproduction in use, and still more methods which have 

 been worked out experimentally but have not yet obtained 

 any commercial status. As regards the application of 

 three-colour heliochromy to process work, we need say 

 no more than to remark that any method of process re- 

 production may be applied to the formation of the triad 

 of printing surfaces from which it is necessary to print 

 in true register with appropriate pigments ; and the 

 question of the successful application of heliochromy to 

 process work depends rather on the colour-sensitising of 

 the negative films, the use of appropriate colour-screens 

 and of suitable printing pigments, than on the purely 

 process side of the work. Those wishing to learn more, 

 or to see representative examples of results, cannot do 

 better than to obtain " The Process Year-Book." 



T, BOLAS. 



NO. 1496, VOL. 58] 



T 



THE FORTHCOMING MEETING OF THE 

 BRITISH ASSOCIATION. 



HE following epitome of the programme of the 

 forthcoming Bristol meeting of the British Associa- 

 tion has been prepared by the Local Secretaries. We 

 have already given a provisional list of the excursions, 

 and shall supply our readers with further details as soon 

 as the routes are finally settled and the arrangements 

 complete. 



Tuesday, September 6. — The Cabot Tower, on Brandon 

 Hill, will be opened at 3 p.m. by the Marquess of Dufferin and 

 Ava, K.P., G.C.B. 



Wednesday, September 7.— Drill Hall Exhibidon opened at 

 3 p.m., by the Marquess of Dufferin and Ava, K.P., G.C.B. 

 Address by the President, Sir William Crookes, F.R.S., in the 

 Colston Hall, at 8 p.m. 



Thursday, September 8. — The Biological Exhibition at the 

 Zoological Gardens, Clifton, will be opened at 3 p.m. by Sir 

 John Lubbock, Bart., M.P. Garden party given by Mr. and 

 Mrs. W. M. Roscoe, at Crete Hill, Westbury-on-Trym, 3.30 to 

 6 p.m. (200). Garden party, given by Mr, E. P. Wills and 

 Miss Wills, at Hazlewood, Sneyd Park, 3.30 to 6 p.m. (200). 

 Conversazione, at Clifton College, given by the Chairman of the 

 Council (the Lord Bishop of Hereford), the Head Master and 

 Mrs. Glazebrook, 8.30 to 11.30 p.m. 



Friday, September 9. — Garden party, given by Mr. and Mrs. 

 Frank Jolly, at Rockwell, Henbury, 3.30 to 6 p.m. (100). 

 Garden party, given by Mr. Lewis Fry, M.P., and Miss Fry, 

 at Goldney House, Clifton, 3.30 to 6 p.m. (300). Garden party, 

 given by Mr. J. Colthurst Godwin and Miss Godwin, at Ellen- 

 thorpe. Stoke Bishop, 3.30 to 6 p.m. (200). Lecture by Prof 

 W. J. Sollas, F.R.S., on "Funafuti: the Study of a Coral 

 Island," in the Colston Hall, at 8 p.m. "Symposium," in 

 honour of the President, Sir William Crookes, F.R.S., at the 

 Merchant Venturers' Technical College, at 10 p.m. (limited 

 to 250). 



Saturday, September 10. — Excursions. Lecture to working 

 men, by Prof E. B. Poulton, F.R.S., "The Ways in which 

 Animals Warn their Enemies and Signal to their Friends," in 

 the hall of the Young Men's Christian Association, at 8 p.m. 

 Public banquet, arranged by the President and members of the 

 Bristol Chamber of Commerce, at the Colston Hall. 



Sunday, September ii. — Special sermons by the Lord Bishop 

 of the Diocese (Cathedral, li a.m.), Prof Bonney (Redcliffe 

 Church, 6.30 p.m.), and Rev. D. Richards, li a.m., and Rev, 

 John Gerard, S.J., 6 p.m. (Pro-Cathedral, Park Place, Clifton). 

 The band of the Royal Artillery (mounted) will perform a 

 selection of music at the Drill Hall, at 3 p.m. 



Monday, September 12. — Garden party, given by the head- 

 master and assistant masters of Clifton College, 3.30 to 6 p.m. 

 Lecture by Mr. Herbert Jackson, on " Phosphorescence," in 

 the Colston Hall, at 8 p.m. 



Tuesday, September 13. — Garden party, given by Mr, and 

 Mrs, Edward Robinson, at The Towers, Sneyd Park, 3,30 to 

 6 p.m, (200). Garden party, given by Mr. and Mrs. G. A. 

 Wills, at Burwalls, Leigh Woods, 3.30 to 6 p,m. (200). Con- 

 versazione at the Colston Hall, given by the Local Committee, 

 8.30 to 11.30 p.m. ' ' 



Wednesday, September 14, — Concluding general meeting, in 

 the Lecture Theatre, Bristol Museum, at 2.30 p.m. Garden 

 party, given by Mr. and Mrs. Herbert Ashman, at Cook's Folly, 

 Sneyd Park, 3,30 to 6 p,m. (200). 



Thursday, September 15. — Excursions. 



Friday, September 16 to 20. — Excursion through Devon- 

 shire, extending over five days Exeter, Torquay,. Dartmouth 

 and Plymouth have taken up the matter very warmly, and 

 kindly offers of hospitable entertainment have been received 

 from them. 



The Committees of the leading Clubs in Bristol and Clifton 

 have consented to grant the privilege of honorary membership 

 to visiting members of the Association during the meeting. 



