1853.] 



SCIENTIFIC INTELLIGENCE. 



141 



likewise some reason to suppose that Foss's bed of hematite in Dover, 

 N.Y., may once have constituted a bed in mica slate. 



In all the Northern States, the beds of this ore occur along the -west- 

 ern base of high mountains ; and fiom the description of the gentleman 

 above named I understand this to be the case in the middle and 

 Southern States. Prof. Henry D. Rogers imputes this fact to the 

 southern direction of the currents in the great ocean by whose waters 

 the iron and the clay were deposited, and to the greater depression of 

 the valley on its south-eastern side. Prof Rogers is the only geologist 

 I believe who speaks decidedly of the deposition of this ore from the 

 ocean. By this suppositimi he comes so near representing this forma- 

 tion as tertiarj', that it would have needed only a bed of carbonaceous 

 matter, such as occurs at Brandon, to have brought him upon that 

 ground. Not improbably, now that the Brandon bed is known, similar 

 ones may be found associated with the ore of other localities : for how 

 long has it remained unnoticed at Braudon I 



Thus does the discovery of the Braudon brown coal deposit enable 

 us to add to American geology a tertiary formation nearly 1200 miles 

 long, which may appropriately be placed upon our maps. 



V. This deposit probably belongs to the Pliocene, or Newer Tertiary. 



1. So far as we know, it lies immediately beneath the drift. 



2. It is destitute of any consolidated beds, save the nodules of hema- 

 tite, which is not true of any of our miocene or eocene deposits. 



3. The brown coal of continental Europe, to which ours corresponds 

 closely in appearance, belongs to the newer tertiary. 



I confess that these arguments are not sufficient to remove all doubts 

 from my mind as to the part of the tertiary group to which this forma- 

 tion should be referred. All geologi.sts, however, I think, will say that 

 it has marked peculiarities, which distinguish it from all the tertiary 

 deposits of our country hitlierto described ; and we may at least say, 

 that the presumption is strongly in favour of its being pliocene. It is 

 rather remarkable, if it was an oceanic deposit, that no marine remains 

 have been found in it. I believe, liowever, that this is very much the 

 case in Germany ; though, uufortunati ly, the papers of Horner, Von 

 Dechan, and others, on the brown coal are not within my reach. 



Photographic Ijandscapcs on Paper. 



32, Harley Street, Dec. 7. 



Allow me to request your insertion in the Atheneetim of the annexed 

 communication, on the subject of Photograjjhy, in the form of a letter 

 to myself from my brother-in-laiv, Mr. John Stewart, resident at Pan ; 

 who has been singularly successful iu his application of that art to the 

 depiction of natural scenery, — and whose representations of the superb 

 combinations of rock, mountain, forest and Avater which abound in the 

 picturesque region of the Pyrenees, are among the most exquisite in 

 their finish, and artistic in their general effect, of any specimens of that 

 art which I have yet seen. The extreme simplicity of the process 

 employed by him for the preparation of the paper, its uniformity, and 

 the certainty attained in the production of its results, seem to render it 

 well worthy of beiug generally known to travelle-s. It need hardly 

 be mentioned that the "air-pump" employed may be one of so simple 

 a construction as to add very little to either the weight, bulk, or ex- 

 pense of the appai'atus required for the practice of this art. The 

 obtaining of a very perfect vacuum, for the imbibition of the paper, 

 being a matter of little moment, — a single barrel (worked by a cross- 

 handle by direct pull and push,) furnished with a flexible connecting 

 pipe, and constructed so as to be capable of beiug clamped on the edge 

 of a table, would satisfy every condition. 



I remain, Ac, 



J. F. W. HERSCHEL. 



Pau, Pyrenees. 

 My Dear Herschel, — Thanks to the valuable indications of Prof 

 Regnault, of the Institid, I have been enabled to produce, what appear 

 to me, most satisfactory results in Photographic Landscapes on Paper. 

 In this remote corner (so deficient also iu resources for experiment) I 

 feel that I am but very partially acquainted with the results obtained 

 and the progress making in the great centres, Paris and London ; but 

 I think that, in detailing the simple process and manipulation I now 

 adopt, indications of some value, and suggestive of further improve- 

 ment to fellow-labourers in the art may be found ; and if you are of the 

 same opinion, you will perhaps facilitate the communication of these 

 details to our photographers at home. 



The following observations arc confined to negative paper processes, 

 divisible into two — the wet and the dry. The solutions I employ for 

 both these processes are identical, and are as follows : — 



Solution of Iodide of Potassium, of the strength of 5 parts of iodide 

 to 100 of pure water. 



Solution of Aceto-Mtrate of Silver, in the following proportions : 

 15 parts of niti'ate of silver ; 21) glacial acetic acid ; 150 of distilled 

 water. 



Solution of Gallic Acid, for developing, a saturated solution. 



Solution of Hyposulphite of Soda ; of the strength of 1 part hypo, of 

 soda, to from 6 to 8 parts water. 



The soluticms employed are thus reduced to their simplest possible 

 expression, for it will be obsei'ved that iu iodizing I employ neither 

 rice-water, sugar of milk, fluorine, cyauogen, nor free iodiue, ifec, &2, ; 

 but a simple solution of iodide of potassium (the strength of this solu- 

 tion is a question of considerable importance, not yet, I think, suffici- 

 ently investigated.) 



For both the wet and the dry processes I iodize my paper , is follows: 

 — In a tray containing the above solution I plunge, one by one, as 

 many sheets of paper (twenty, thirty, fifty, &c..,) as are likely to be 

 required for some time. This is done iu two or three minutes. I then 

 roll up loosely the whole bundle of sheets, while in the bath ; and 

 picking up the roll by the ends, drop it into a cylindrical glass vessel 

 with a foot to it, and pour the solution therein, enough to cover the 

 roll completely (in case it should float up above the surface of the 

 solution, a little piece of glass may be pushed down to rest across the 

 roll of paper and prevent its rising.) The vessel with the roU of pa- 

 per is placed under the receiver of an air pump and the air exhausted ; 

 this is accomplished in a very few minutes, and the paper may then 

 be left five or six minutes iu the vacuum. Should the glass he too 

 high (the paper being in large sheets) to be inserted under a pneuma- 

 tic pump receiver, a stiff lid lined with Indi.-i rubber, with a valve iu 

 the centre communicating by a tube with a common direct-action air- 

 pump may be employed with equal success. After the paper is thus 

 soaked in vacuo it is removed, and the roll dropped back into the tray 

 with the solution, and then sheet by sheet picked off and hung up 

 to dry, when, as with all other iodized paper, it will keep for an inde- 

 finite time. 



I cannot say that I fully understand the rationale of the action of 

 the air-pump, but several viiluable advantages are obtained by its use : 

 . — 1st. The paper is thoroughly iodized, and with an equality through- 

 out that no amount of soaking procures, for no two sheets of paper are 

 alike, or even one, perfect throughout in texture ; and air bulbs are 

 impossible. 2nd. The operation is accomplished in a quarter of an 

 hour, which generally employs one, two, or more hours. 3rd. To this 

 do I chiefly attribute the fact that my paper is never .solarized even in 

 the brightest sun ; and that it Avill bear whatever amount of exp.-sure 

 is necessary for the deepest and most impenetrable shadows in the 

 view, without injury to the bright lights. 



Wet Process.— To begin with the leet process. Having prepared the 

 above solution of aceto-nitrate of silver, float a sheet of the iodized 

 paper upon the surface of this sensitive bath, leaving it there for about 

 ten minutes. During this interval, having placed the glass or slate of 

 your slider quite level, dip a sheet of thick clean white printing (un- 

 sized) paper in water, and lay it on the glass or slate as a wet hningto 

 receive the sensitive sheet. An expert manipulator may then, remov- 

 ing the seusitive sheet from the bath, extend it [sensitive side upper- 

 most] ou this wet paper lining, without allowing any air gloTjulcs to 

 intervene. But it is difficult, and a very simple and most effectual 

 mode of avoiding air globules, particularly in handling very large sheets, 

 isasfollows:— Pour a thin layer of water [just sufficient uot to flow over 

 the sides] upon the lining paper, after you have extended it on your glass 

 or slate, and then lay down your sensitive paper gently aud by degrees, 

 and floating as it were on tifiis layer of water ; and when extended, 

 taking the glass and papers between the finger and thumb, by an 

 upper coruer, to prevent their slipping, tilt it gently to allow the inter- 

 posed water to flow oft' by the bottom, which wiU leave the two sheets 

 of paper adhering perfectly and closely, without the slightest chance 

 of air-bubbles :— it may then be left for a minute or two, standing up- 

 right in the same position, to allow every diop of water to escape ; so 

 that when laid flat again or placed in the shder none nnay return back 

 aud staiu the paper. Of course, the sensitive side of the sheet is thus 

 left exposed to the uninterrupted action of the lens, no protecting plate 

 of glass being interposed, — aud even in this dry and warm climate I 

 find the humidity and the attendant sensitiveness fully preserved for a 

 couple of hours. 



To develope views thus taken, the ordinary saturated solution of 

 gallic acid is employed, never requiring the addition of nitrate of silver; 

 thus preserving the perfect purity and varied modulation of the tints. 

 The fixing is accomplished as usual with hyposulpliite of soda, and the 

 negative finally waxed. 



Dry Process.— la preparing sheets for use -when dry for travelling, 

 (fee, I have discarded the use bf previously waxtd paper,— thus getting 

 rid of a troublesome operation, — and proceed as follows : Taking a sheet 

 of my iodized paper, in place of floating it (as for the wet process) on 



