1854] 



PHOTOGRAPHY— THE 



downwards as well as upwards in as great, if not greater, pro- 

 portion. So far as our Tennessee species are concerned, it 

 would be a much more Natural arrangement to unite tbo lower 

 part of the Trenton limestone with the Black River rocks, and 

 the central and upper portions with the Hudson River group. 

 The Table, which has been constructed with reference to this 

 view, illustrates this point sufficiently well. Most of the Tren- 

 ton species in the Stones River group belong to the Lower 

 division, and the few others may be found hereafter to belong to 

 the same; while all of the Trenton species, in the Nashville 

 group, belong to the Upper division three of them being 

 common. 



If the New York species will admit of this classification, 

 and we are inclined to think they will, the confusion, which has 

 hitherto existed in regard to the parallelism of these groups, will 

 in some measure, at least, be removed. 



The parallelism will then be — 



Hudson River, ) 



Nashville group. •] Utica State, V New group. 



Cen. and Up. Trenton. ) 



t,, -r, 1 Jjower j. rem 



SfconesR -S rou Pi Black R.G. 



Lower Trenton, 



New group : 



say 

 Black River. 



Photography— The Wax-Paper Process. 



May I ba permitted to detail a process I have found very 

 successfid during a photographic tour I have taken this autumn ? 

 It combines the advantages of extreme sensitiveness • (two 

 minutes being as effectual as ten by the ordinary method), 

 together with the faculty of the excited paper keeping good for 

 several weeks; two properties which I consider invaluable while 

 working at a distance from home, as the papers can all be 

 excited ready for the camera before commencing the journey, 

 while the development can be deferred until the return home, 

 provided the time elapsed after exciting be not more than about 

 three weeks. By this means the necessity for carrying about a 

 quantity of dishes, chemicals, etc., is avoided, the only requisites 

 being ihe camera and stand, paper holders and prepared paper. 



My method is a modification of Le Gray's process, in' which 

 the pores of the paper are saturated with wax previous to the 

 formation of the surface. This is undoubtedly the best, both as 

 regards the brilliancy of the finished picture, and the ease and 

 convenience of manipulation ; but there are several circumstances 

 which tend to impair the beauty of the result, foremost of which 

 may be mentioned the spots, one or two being generally to be 

 met with even on the best paper, By the following slight 

 modification I have succeeded in removing the impurities which 

 cause the spots, and also in diminishing the time of exposure in 

 the camera. 



The paper I employ is the thin variety made by Canson, 

 Freres. The first operation consists in waxing it : the sheets, 

 cut to the proper size and marked on the smooth side, are to bo 

 soaked in melted wax, and afterwards separately ironed between 

 blotting paper until there are no shining particles of wax to be 

 seen on the surface. 



The next operation consists in iodizing the sheets ; the bath is 

 composed of 



Iodide of potassium 15 grains. 



"Water 1 pint imp. 



WAX-PAPER PROCESS. i*& 



with the addition of as much free iodine as will give it a sherry 

 color. This removes the iron and brass, of which the spots 

 generally consist: it will require renewing now and then. The 

 sheets are to be completely immersed in tins bath for at least two 

 hours, taking care to avoid air bubbles, and then hung up to 

 dry : they will be of a deep purple color, owing partly to the 

 union of the iodine with the starch in the paper, and will keep 

 good any length of time. 



The solution for rendering these iodized sheets sensitive con 

 sists of 



Nitrate of silver 15 grains 



Glacial aoetic acid 15 " 



Water l ounce. 



The marked side of the paper is to be laid carefully on this 

 solution, and kept there for about half a minute longer than 

 necessary to completely decolorize it (from seven to ten minutes), 

 and then floated on distilled water for a few minutes. It must 

 then be dried between blotting-paper, and kept in perfect dark- 

 ness in a portfolio until required. With only one washing in 

 distilled water, as above, it will not keep good longer than six 

 days ; but if washed sufficiently it will keep good for weeks. 



It is hardly possible to state any definite time for the exposure 

 in the camera, as this of course must vary with the intensity of 

 the light ; but with a lens of twelve inches focal length, with a 

 ha'f inch aperture in front of it, from one to two minutes will 

 suffice on a bright day with the sun out ; while on a dark 

 gloomy day, from seven to ten minutes may be requisite. 



For developing the picture, I employ four parts of a nearly 

 saturated solution of gallic acid, and one part of the solution 

 previously employed for exciting the paper; these are well 

 mixed, and the marked side of the paper floated on it. The 

 picture will soon begin to appear, and should be completely out 

 in less than an hour, and before the gallo-nitrate is decomposed ; 

 it must then be washed, soaked in tolerably strong hyposulphite 

 of soda until all the yellow iodide is removed, washed again 

 several times, and then dried, and either ironed over, or held 

 before a fire to melt the wax. The greatest care must be taken 

 to have the dish perfectly clean to contain the gallo-nitrate ; it 

 ought to be rubbed with strong nitric acid now and then, to 

 remove the stains from a previous operation ; unless this precau- 

 tion be taken to avoid the presence of dirt the picture will be 

 covered with stains similar to lrurbling in book- binding. The 

 gallic acid and nitrate of silver must also be filtered before 

 mixing. 



By adhering to these directions, any person who has a little 

 experience in manipulation may be sure of getting excellent 

 results, with a far less number of failures than by any other pro- 

 cess. I have endeavored to state everything as explicitly a? 

 possible, but should I not have rendered myself sufficiently 

 intelligible in any part of the process, I shall be happy to give 

 any information that lays in my power. 



William Crookes. 

 Hammersmith. 



P. S. — I have seen several inquiries respecting the price that 

 ought to be paid for a good lens, the general idea seeming to be 

 that they are very expensive. The lens I always employ cost 

 me fifteen shillings ; it was made at Slater's, and is If inch in 

 diameter, and 12 inches focus. The picture I forward as an 

 illustration of the process will show what can be done with it : 

 it was taken in one minute with a half inch aperture in front of 

 the lens. — Notes and Qucrkn. 



