[By the courtesy of our valued cotemporary _The Athenaeum_, we are
permitted to reprint the following interesting communication, which
appeared in that journal on Saturday last.]
"NEW PHOTOGRAPHIC PROCESS.
"Henley Street, July 6.
"Your insertion of the annexed letter from my brother-in-law, Mr. John
Stewart, of Pau, will much oblige me. The utility of this mode of
reproduction seems indisputable. In reference to its concluding paragraph,
I will only add, that the _publication_ of concentrated microscopic
editions of works of reference--maps, atlases, logarithmic tables, or the
concentration for pocket use of private notes and MSS., &c., &c., and
innumerable other similar applications--is brought within the reach of any
one who possesses a small achromatic object-glass of an inch or an inch and
a half in diameter, and a brass tube, with slides before and behind the
lens of a fitting diameter to receive the plate or plates to be operated
upon,--central or nearly central rays only being required. The details are
too obvious to need mention.--I am, &c.
"J. F. W. HERSCHEL.
* * * * *
"Pau, June 11.
"Dear Herschel.--I sent you some time ago a few small-sized studies of
animals from the life, singly and in flocks, upon collodionised glass. The
great rapidity of exposition required for such subjects, being but the
fraction of a second, together with the very considerable depth and harmony
obtained, gave me reason to hope that ere this I should have been able to
produce microscopic pictures of animated objects. For the present, I have
been interrupted. Meantime, one of my friends here, Mr. Heilmann, following
the same pursuit, has lighted on an ingenious method of taking from glass
negatives positive impressions of different dimensions, and with all the
delicate minuteness which the negative may possess. This discovery is
likely, I think, to extend the resources and the application of
photography,--and with some modifications, which I will explain, to
increase the power of reproduction to an almost unlimited amount. The plan
is as follows:--The negative to be reproduced is placed in a slider at one
end (_a_) of a camera or other box, constructed to exclude the light
throughout. The surface prepared for the reception of the positive--whether
albumen, collodion, or paper--is placed in another slider, as usual, at the
opposite extremity (_c_) of the box, and intermediately between the two
extremities (at _b_) is placed a lens. The negative at _a_ is presented to
the light of the sky, care being taken that no rays enter the box but those
traversing the partly transparent negative. These rays are received and
directed by the lens at _b_ upon the sensitive surface at _c_, and the
impression of the negative is there produced with a rapidity proportioned
to the light admitted, and the sensibility of the surface presented. By
varying the distances between _a_ and _c_, and _c_ and _b_, any dimension
required may be given to the positive impression. Thus, from a medium-sized
negative, I have obtained negatives four times larger than the original,
and other impressions reduced thirty times, capable of figuring on a
watch-glass, brooch, or ring.
"Undoubtedly one of the most interesting and important advantages gained by
this simple arrangement is, the power of varying the dimensions of a
picture or portrait. Collodion giving results of almost microscopic
minuteness, such negatives bear enlarging considerably without any very
perceptible deterioration in that respect. Indeed, as regards portraits,
there is a gain instead of a loss; the power of obtaining good and pleasing
likenesses appears to me decidedly increased, the facility of subsequent
enlargement permitting them to be taken sufficiently small, at a sufficient
distance (and therefore with greater rapidity and certainty) {61} to avoid
all the focal distortion so much complained of,--while the due enlargement
of a portrait taken on glass has the effect, moreover, of depriving it of
that hardness of outline so objectionable in a collodion portrait, giving
it more artistic effect, and this without quitting the perfect focal point
as has been suggested.
"But there are many other advantages obtained by this process. For copying
by engraving, &c. the exact dimension required of any picture may at once
be given to be copied from.
"A very small photographic apparatus can thus be employed when a large one
might be inconvenient or impracticable, the power of reproducing on a
larger scale being always in reserve. Independent of this power of varying
the size, positives so taken of the _same_ dimension as the negative
reproduce, as will be readily understood, much more completely the finer
and more delicate details of the negatives than positives taken by any
other process that I am acquainted with.
"The negative also may be reversed in its position at _a_ so as to produce
upon glass a positive to be seen either upon or under the glass. And while
the rapidity and facility of printing are the same as in the case of
positives taken on paper prepared with the iodide of silver, the negatives,
those on glass particularly, being so easily injured, are much better
preserved, all actual contact with the positive being avoided. For the same
reason, by this process positive impressions can be obtained not only upon
wet paper, &c., but also upon hard inflexible substances, such as
porcelain, ivory, glass, &c.,--and upon this last, the positives being
transparent are applicable to the stereoscope, magic lantern, &c.
"By adopting the following arrangement, this process may be used largely to
increase the power and speed of reproduction with little loss of effect.
From a positive thus obtained, say on collodion, _several hundred_
negatives may be produced either on paper or on albumenised glass. If on
the latter, and the dimension of the original negative is preserved, the
loss in minuteness of detail and harmony is almost imperceptible, and even
when considerably enlarged, is so trifling as in the majority of cases to
prove no objection in comparison with the advantage gained in size, while
in not a few cases, as already stated, the picture actually gains by an
augmentation of size. Thus, by the simultaneous action, if necessary, of
some hundreds of negatives, many thousand impressions of the same picture
may be produced in the course of a day.
"I cannot but think, therefore, that this simple but ingenious discovery
will prove a valuable addition to our stock of photographic manipulatory
processes. It happily turns to account and utilises one of the chief
excellencies of collodion--that extreme minuteness of detail which from its
excess becomes almost a defect at times,--toning it down by increase of
size till the harshness is much diminished, and landscapes, always more or
less unpleasing on collodion from that cause, are rendered somewhat less
dry and crude.
"A very little practice will suffice to show the operator the quality of
glass negatives--I mean as to vigour and development--best adapted for
reproducing positives by this method. He will also find that a great power
of correction is obtained, by which overdone parts in the negative can be
reduced and others brought up. Indeed, in consequence of this and other
advantages, I have little doubt that this process will be very generally
adopted in portrait taking.
"Should your old idea of preserving public records in a concentrated form
on microscopic negatives ever be adopted, the immediate positive
reproduction on an enlarged readable scale, without the possibility of
injury to the plate, will be of service.
"I am, &c. "JOHN STEWART."
* * * * *
Replies to Minor Queries.
_The Ring Finger_ (Vol. vii., p. 601.).--The Greek Church directs that the
ring be put on the right hand (Schmid, _Liturgik_, iii. 352.: Nassau,
1842); and although the direction of the Sarum _Manual_ is by no means
clear (see Palmer's _Origines Liturgicae_, ii. 213., ed. 2.), such may have
formerly been the practice in England, since Rastell, in his
counter-challenge to Bishop Jewel, notes it as novelty of the
Reformation,--
"That the man should put the wedding-ring on the fourth finger in the
left hand of the woman, and not on the right hand, as hath been many
hundreds of years continued."--Heylyn, _Hist. Ref._, ii. 430. 8vo. ed.
But the practice of the Roman communion in general agrees with that of the
Anglican. (Schmid, iii. 350-2.) Martene quotes from an ancient pontifical
an order that the bridegroom should place the ring successively on three
fingers of the right hand, and then shall leave it on the fourth finger of
the left, in order to mark the difference between the marriage ring, the
symbol of a love which is mixed with carnal affection, and the episcopal
ring, the symbol of entire chastity. (_Mart. de Antiquis Eccl. Ritibus_,
ii. 128., ed. Venet. 1783; Schmid, p. 352.)