20 



NEW PROCESS OF PHOTOGRAPHIC ENGRAVING ON STEEL. 



[1853 



.June 4th 



Agricultural Association of Lower Canada. The AnDual Exhibition of 

 the Agricultural Association of Upper Canada, will take place in the 

 City of Hamilton, ou October 4th, 5th, Oth and 7th. Both exhibitions 

 will be open to competition from all parts of United Canada. 



Naturalists' Calendar. 



For April, May, June and July, Toronto, 1853. 

 By William Cower. 



butterflies: First seen. 



Camberwcll Beauty, . ..Vanessa Antiopa April 9th 



Black Swallow-tail, Papilio Asterius " 



Clouded Sulphur, Coiias PhUodicc, " " 



Orange Comma, Grapia o Album, " " 



Grey Vined White, Pontia Oleracca, May 14th 



Tiger Swallow-tail, Papilio Turmis, " 28th 



Small Copper, Lyeana PItJcas, " 29th 



Black Skipper, Thpnele Prim? 



Small Spotted Meadow Brown,. Hipparclda t 



Spring Azure Polyommatus Lucia " " 



The Archippus Panais Archippus, " 6th 



Pearl-border Fritillary, Mclilaa Myrina, " 10th 



Banded Purple Limenitis Arthemis, " " 



Baltimore Fritillary, Mclitaa Phacion, " 15th 



motus: 



Great Satumia (class Attaci) issue from cocoon, May 24th 



Saturnia Polyphemus issue from cocoon, " 25th 



Saturnia Prometheus issue from cocoon, June 6th 



Ghost Moth, Hipiolus Jlumuli, " " 



Royal Tiger Aretia Virgo, " 9th 



Buff Leopaid,... Aretia Isabella, " 14th 



Twin-eyed Hawkmoth, Smerinthvs Gcminatus " 20th 



Eyed Hawkmoth, Smerinthus Ocel/atus, " 24th 



Panther, Spilosoma Acria " " 



Silver-spotted Buff, Pyr/ccra Gibbosa, July 8th 



Zebra Hawkmoth, Sphinx Kahniat, " 27th 



Grey Hawkmoth, Sphinx Cinerca,, " " 



birds: 

 Little Grebe, (Colymbus Minor,) begins to build its nest — 



lays six whitish eggs, April 30th 



Ground Lark, begins to build its nest, " 7th 



Humming-birds, May 7th 



Red-winged Stalling, (Sturuus Prcdatorius,) begins to build 



its nest, .May 18th 



Whip-poor-will Caprhmdgus Vocifcrus June 19th 



miscellaneous: 

 Gall-flies, (Cynips Quercus folii) deposit their ova in the 



leaves of the Oak, .•. ]yr a y ggf^ 



Racoon shot in the neighbouring woods, " ]4th 



Tree Frog, (Ilyla Versicolor,) « oj s t 



Ephemera Bioculata, with two satfe at the tail, longer than 



the body, Jlme Ml 



Field Cricket, (Ac/icta Campestris,) pipes its evening song, " " 

 Star crane-fly, {Bittacomorpha Crassipcs) deposits its ova in 



the earth « jj^ 



Cuckoo-spit Insect, Tdli/jonia Spumaria " 



Rattling Locust, (Fdipoda Sidp/mrca? " " 



Firefly, a Zampyris Corusca, " 13th 



Wild Strawberries {Fragaria Virginiana,) ripe " 11th 



Blue-berries, ripe ....July 8th 



Tree-hop2>ing Locust, Cicada ? " 13^ 



Wild Raspberries, {Rubus Ucbus) ripe, " " 



Wild Blackcurrant, (Ribes Floridum?) ripe ... " 23th 



Wild Gooseberry, (Jiibes Cynosbati,) ripe.... " 30th 



Wild Blackberry, {RubusPlispidus,) ripe . . . " " 



New Process of Photographic Engraving oa Slecl. 



Bl' ME. FOX TALBOT. 



I now proceed to give you an account of my newly invented method 

 of makiug photographic engravings upon steel. Of course, I have no 

 need to observe that the art is at present in its infancy, but I have 

 great hopes that it will very soon be considerably improved in all its 

 details. 



The first thing to be. done is to select a good steel plate, and to im- 

 merse it for a minute or two in a vessel containing vinegar mixed with 

 a little sulphuric acid. The object of this is to diminish the too great 

 polish of the surface; for otherwise the photographic preparation 

 would not adhere well to the surface of the steel, but would peel off. 

 The plate is then to be well washed and dried. Then, take some isinglass 

 and dissolve it in hot water. The solution should be strong enough 

 to coagulate when cold into a firm jelly. This solution of isinglass or 

 gelatine should be strained while hot through a linen cloth to purify 

 it. To this must be added about half as much of a saturated solution 

 of bichromate of potash in water, and they should be well stirred to- 

 gether. When cold, this mixture coagulates into a jelly, which has 

 very much the appearance of orange jelly. The method of using it is, 

 liquify it by geutle heat. Then take a glass rod, hold it horizontally, 

 aud spread the liquid uuiformly over the plate. Then incline the plate 

 and pour off the superfluous gelatine. Let the steel plate be placed 

 upon a stand, aud kept quite horizontal, that the liquid may not run 

 to one side of the plate. Then place a spirit lamp beneath the plate, 

 and warm it gently till the gelatiueis quite dried up. When dry, the 

 film of the gelatine ought to be bright yellow and very uniform. If 

 clouded bauds appear upon the surface it is a sign that there is too 

 little gelatine in proportion to the bichromate, which must therefore 

 be corrected. The steel plate, now coated with gelatine, is ready to 

 receive a photographic image of any object First, let us suppose the 

 object is one capable of being applied closely to the surface of the plate ; 

 for instance, let it be a piece of black lace or the leaf of a plant. Place 

 the object upon the plate in a photographic copying frame, and screw 

 them into close contact. Place this frame in the direct light of the 

 sun for a short time, varying from half a minute to five minutes. Let 

 it then be removed and the plate taken out, and it will be found im- 

 pressed with a yellow image of the object upon a grouud of a brow- 

 color, as might be expected from the well known photographic proa 

 perty of bichromate. The plate is then to be placed in a vessel of cold 

 water for a minute or two, which dissolves out all the bichromate and 

 most of the gelatine also from the photographic image, i. c. from those 

 parts of the plate which have not been exposed to the sun, being pro- 

 tected by the object; while, on the contrary, it dissolves little or none 

 of the gelatine film which has been fully exposed to the sun's rays. 

 The consequence of whibh is, that instead of a yellow image we have 

 now a white one, but still upon a ground of brown. The plate is then 

 removed from the water into a vessel of alcohol for a minute, and it is 

 then taken out and placed upright on its, edge in a warm place, where 

 in the course of a few minutes it becomes entirely dried. This termi- 

 nates the photographic part of the operation. If the plate is carefully 

 examined while in this state, it appears coated with gelatine of a yel- 

 lowish brown color, aud impressed with a white photographic image, 

 which is often eminently beautiful, owing to the circutustauce cf its 

 being raised above the level of the plate by the action of the water. 

 Thus, for instance, the image of a piece of black lace looks like a real 

 piece of very delicate white lace of similar pattern, closely adhering to, 

 but plainly raised above, the brown and polished surface of the plate, 

 which serves to display it very beautifully. At other times the white 

 image of an object offers a varying display of light when examined by 

 the light of <t single caudle, which indicates a peculiar molecular ar- 

 rangement in the particles of gelatine. These photographic images 

 are often so beautiful that the operator feels almost reluctant to des- 

 troy them by continuing the processs for engraving the plate. 



In order to explain how such an engraving is possible, it is, in the 

 first place, to be observed that the photographic image differs from 

 the rest of the plate not only in color, but, what is of much more im- 

 portance, in the thickness of the film of gelatiue which covers it. The 

 coa'ing of gelatiue on the rest of the plate is, comparatively speaking, 

 a thick one, but that which originally covered the image has been 

 mostly removed by the action of the water, a small portion, however, 

 almost always remaining. It therefore naturally happens that when 

 au etching liquid is poured on the plate, it first penetrates through the 

 thin gelatiue covering the image, and etches the steel plate beneath. 

 But the next moment it penetrates likewise through the thicker coat- 

 ing of gelatine, and thus spoils the result by etching the whole of the 

 plate. Nitric acid, for instance, does this, and therefore caunot be em- 

 ployed for the purpose. Since the other chemical liquids which are 

 capable of etching steel have a certain analogy to nitric acid in their 

 corrosive properties, they also for the most part are found to fail in the 

 same manner. 



