This is a reprint of extracts from
Kerr, Richard and Arthur E. Smith. Nature through Microscope and Camera. London: The Religious Tract Society, 1905.
These extracts emphasize photography and microscopy rather than nature.
The transcribed text does not preserve the line breaks of the original, save in a few unusual places.
Scanned in 2003.
The transcribed sections follow below.
CHARLES KINGSLEY has said, 'I have seen the cultivated man craving for travel, and for success in life, pent up in the drudgery of London work, and yet keeping his spirit calm, and perhaps his morals all the more righteous, by spending over his microscope evenings which would too probably have been gradually wasted at the theatre.'
This is strong testimony to the value of the microscope alone as an entertaining and civilising instrument. But the value of the instrument is increased enormously by the addition of the photographic camera. It is not at all necessary to have a huge camera like that represented in the illustration (Fig. 8). But of this we shall say something later.
[p.] 17
The uppermost thought in the minds of those who engage in photomicrography, even in an elementary way, is, I fancy, What a vast amount of intellectual pleasure people miss who have no knowledge of these instruments, people too who could well afford to have them, and who, if so inclined, could use them with advantage in quarters where valuable time and money are spent at 'Bridge,' and where the powers of conversation rise no higher than in ecstatic admiration of some fancy dog.
'To Amuse, and not to Educate,' is an announcement we see on the hoardings. It expresses the spirit of the times in England. Amusement is the order of the day in dear old England; and other nations love to have it so, because the more we' fool away' our time the more they employ their time and talents in raising the intellectual status of their countries, and as a result their commercial prosperity follows. Theyare to be commended, while our case is to be deplored.
It is not hinted for one moment that games and amusements should be abolished; such a
suggestion would be absurd. But we cannot shut our eyes to the fact that there can be too much of the amusement fetich [sic]. It is overdone, and its devotees act as if the only aim in life is to be amused. The prosperity of the nation does not depend upon the amount of amusement that can be crammed into our lives, but upon the intellectual attainments of the units that make up the nation.
There are hundreds of thousands of people in certain counties [sic; not "countries"] whose whole conversation is permeated with football and cricket language, showing the uppermost and paramount thoughts in their minds.
It is not at all unlikely that this 'amusement and not education' desire is the cause of our trade finding its way barred by better work by other peoples, the cause of a good deal of the want of employment among our working classes, and the direct or indirect cause of an amount of poverty and crime.
There are too many places of amusement in our cities, too many trashy and pernicious novels read in our free libraries, too much time
given to games, both in the upper and in the working classes, and not enough time nor attention given to those forms of intellectual recreation which improve the mind. Our boys are made physically strong, but is the mental development keeping pace with the physical? If not, our nation will deteriorate.
We do not suggest photography through the microscope as the remedy for existing defects, but we think that the more our young men take up intellectual pastimes the better it will be for the nation. This is one of those pastimes. It is not a selfish one. One enthusiast is a centre of usefulness to others, for he cannot keep to himself the enjoyment he receives from the study of Nature's beauties and wonders.
A section of the book is devoted to histological subjects intended specially for aunior medical students. At the same time the illustrations and descriptions of all the subjects in this particular department ought to be familiar to every one. The enormous work done by the heart, the wonderful structure
of a human hair, and that of the skin, &c., are all points well worth our attention. There is nothing in Nature, so far as we know it, that is more wonderful than the human body, even considered from the histologist's standpoint. Our education is incomplete if we have shunned all knowledge of our own system and its wonders.
The illustrations are entirely original. Nothing from these negatives has ever been published excepting the 'spider's foot,' which appeared in the July number of 'Knowledge' as a whole-page illustration.
An expression of our indebtedness is due to Mr. Henry Tavener for his new discovery and his permission to illustrate it - the Mideopsis orbicularis of pond water; also to Dr. Joseph A. Featherstone, of Tooting, for his kindness in describing the histological details of several sections illustrated.
RICHARD KERR.
The Illustrations.
THE illustrations have been taken from photo-micrographs [hyphen in original word; not a line break] done on 12 by 10 plates directly through the microscope and camera combined as one instrument. The negatives have received no 'touching-up' whatever.
They were exhibited at the Royal Society's Annual Conversazione, May 13,1904. In the catalogue is the following summary of the exhibit :-
'Examples of Photo-Micrography. The exhibit includes sections of histological, botanical, and entomological specimens, intended to assist
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students of biology generally and medical students especially. The camera used is unusually large in order to ensure direct photography. In no case are the results produced from the enlargement of small negatives.'
Subsequently we were invited to exhibit them at the Conversazione of the London University held at the Imperial Institute, May 27.
When photographs are enlarged from small negatives there is no material gain as regards new details. The advantage of a large camera (Fig. 3) is shown in several of the illustrations where a vast amount of design is visible which could not be secured by ordinary enlargements.
We are well aware that with the electric light or even the oxy-hydrogen lime-light, time could be saved as regards the exposures; but for general workers it is better to show what can be done with ordinary means of illumination, than to lead them to think that the electric or other light is indispensable.
The extra large camera is not absolutely necessary in all cases of photo-micrography,
but for certain diatoms and other objects that display excessively minute structure it has its advantages, some of which, we hope, are apparent in the illustrations.
Excellent results have been obtained by primitive or homely methods and appliances. In fact two or three boxes telescopically arranged will answer all the ordinary purposes of an elaborate camera fitted with long bellows.
In photographing the features of the human being it is customary to submit the negatives to a system of re-touching [again, hyphen in original word]. The photographers would do very little of this were it not for the vanity of their customers, and they would do very little photography if they were to omit the re-touching process.
But as regards the photography of microscopic objects it is a mistake to add any line or to make any object look as we would wish it to look. Drawings from microscopic objects often betray this defect.
No artists' license should be resorted to beyond reducing the density of, or strengthen-
ing the negative. The personal equation must be left out, for it is hardly likely that any naturalist can suggest an improvement in the design of a diatom, of a radiolarian, or of a section of an ordinary plant. Laplace, the famous French astronomer, and undoubtedly one of the greatest astronomers of any nation, thought he could suggest a much better position in the heavens for the Moon (see Richard Proctor's The Expanse of Heaven, chap. ii.). Similarly, to judge by the interpretation put by some on the structure of minute forms of life, daring, if not conceit, manifests itself in a surprising degree.
Shakespeare teaches us all a lesson on this point :-
'To gild refined gold, to paint the lily,
To throw a perfume on the violet,
To smooth the ice or add another hue
Unto the rainbow, or with taper-light
To seek the beauteous eye of heaven to garnish,
Is wasteful and ridiculous excess.'
What is the highest magnification obtained with the modern microscope?
This is a question the microscopist is frequently asked.
Two answers can be given to that question.
Those unacquainted with the use of the microscope will bear in mind that students of that instrument never speak of the superficial area of any microscopic amplification; it being understood by them that dimensions are always to be expressed in diameters only.
Those who, at the Royal Society's recent Conversazione, were privileged to see the "High Power Microscopy," by Mr. J. W. Gordon, must have realised that microscopy had made a decided step forward by that gentleman's in- vention.
The answer, or one of the answers to the above question, will be apparent from a brief consideration of Mr. Gordon's ingenious methods.
He had two microscopes. In the field of
3
view of one he placed an opalescent screen which he kept oscillating to serve as a secondary source of radiation and to expand the transmitted wave front, causing it to fill the aperture of the second microscope. This latter instrument gave a further magnification of 100 diameters. The oscillation of the ground glass or opalescent screen removed the imperfections of excessive magnification and rendered invisible its own grain. A diatom (Pleurosigma angulatum) was exhibited, and showed an amplification of 10,000 diameters. Its markings were clearly defined.
When we remember that this particular diatom is practically invisible to unassisted eyesight, and that its highest amplification in Dr. Dallinger's edition of Carpenter's Microscope and its Revelations is 4,300 diameters, we cannot but realise that a very distinct advance has been made.
To suggest a second answer to the question propounded, I must refer to diffraction gratings or microscopic rulings.
Lines have been ruled by extremely deli-
cate instruments on speculum metal up to 14,000 lines, and even more, per inch, but so far Mr. Grayson has far surpassed all other records in microscopic rulings. His plates contain 120,000 lines per inch.
Mr. E. M. Nelson, one of the greatest authorities on microscopic research, tells us his experience in resolving those lines; it need hardly be said that such fine work requires uncommonly good microscopic powers and excellent illumination for their resolution. Mr. Nelson found that he could resolve strongly the 120,000th band with a 1/8th inch oil immersion lens; he also resolved the same lines with a cheap 1/10th inch oil immersion.
The 90,000th band he resolved with the 1/6th inch, and also with a Powell and Lealand's best 1/4 inch; and the 60,000th band with a Zeiss 1/2 inch. (Royal Micros. Journal, 1904).
The rulings are mounted in realgar, and are more difficult to resolve than diatoms of equal fineness.
This being Mr. E. M. Nelson's experience, the statement made in the latest works on
optics used in the Universities that 'the theoretical limit of microscopical vision is the 1/90000th of an inch' is hardly correct, inasmuch as 120,000 lines, or 1/3rd more, can actually (not theoretically) be seen showing up strongly with a 1/8th inch oil immersion, which is by no means a very high-power objective nowadays.
Although the high amplification of 1,000 diameters is not an extensive limit to the powers of the microscope, yet, beyond this, the objectives must be higher than the 1/12th inch, and the eye-pieces of the highest power.
Only a few, who may be looked upon as specialists in microscopy, ever exceed this range of magnification.
Several of these illustrations are from nega- tives of much higher amplification than 1,000 diameters, but in these cases the camera has augmented the work of the microscope.
A MICROSCOPE slide for photographic purposes should be perfect and the object typical. An imperfect slide is difficult to photograph and never looks well.
The starting point is to place the slide in the microscope and see exactly what is required to be photographed; the microscope can then be placed horizontally and the lighting arranged so that the effect seen when viewed through the tube is exactly what is required to appear in the photograph. (Fig. 7).
It is well and convenient to have the camera and microscope adapted to a rigid and perfectly straight base and in such a manner
* This chapter is contributed by Arthur E. Smith.
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that the camera may be easily lengthened or shortened.
If the camera can be placed on runners or in a sliding groove to allow of its being moved aside while the object is being illuminated and adjusted in the microscope it will be a decided advantage.
This done, the front of the camera should be brought up to the eye-piece end of the microscope. The point of junction must be made light-tight, and the whole fixed so that the two instruments are, for the time being, practically one.
There will now be some sort of an image on the ground glass, and a slight adjustment of the focus ought to make that image sharp.
A long rod or a cord can be placed along the length of the camera and adapted to work the adjustment-screw of the microscope in either direction, as shown in the illustration (Fig. 8).
For the low and medium powers a focussing glass can be used with great advantage, but with very high powers when the image is dim the £ocussing can be better
done with the naked eye or with a very low-power [hyphen in original, at a line break] magnifier.
The magnification should be carefully ascertained and marked on each negative. For lower powers this is easily found by using a thin piece of metal with, say, a 1/8th inch hole bored through it. When the photograph is taken and the microscope slide removed, the piece of metal is placed on the stage of the microscope. The image of the hole falls on the ground glass screen, and its amplification can be easily ascertained.
With high powers a micrometer must be used. This is a glass slide with lines ruled on it, the 1/100th and 1/1000th of an inch apart. This is focussed as in the former instance on the ground glass screen. If the lines of the 1/100th divisions appear 2 inches apart, then its magnification is 200 diameters. If the lines of the 1/1000th division appear, say, 3 inches apart, the magnification will be 3,000 diameters.
A convenient method is to have the support of the camera graduated in inches and parts of an inch. In this way the amplification
would be known without measuring each time.
The focussing cloth may be used in the usual way for low powers, but is almost out of the question for high powers. With very high powers the best way is to have a special perfectly dark room for the camera.
The Developer, Plates, &c.
A convenient developer is that originally issued as the Ilford Universal Developer, but somewhat modified for ease of mixing.
Very weak images to low magnifications can advantageously be produced on process plates, as these give great contrast.
The higher magnifications must be done on quick plates.
The exposures vary from two seconds to about two hours, or even longer. These long exposures of the higher powers are very difficult to keep free from vibration. The slightest shake, as a matter of course, spoils the negative. A good condenser will materially shorten the exposure.
Isochromatic plates are generally most useful, as with the object stained purple, which is usually the case, a yellow screen has to be used between the light and the object to make the purple come out much stronger . At the same time it increases the exposure four to six times, according to the density of the yellow glass screen. The yellow screen can also be used to reduce contrast where part of the image is yellow. Take as an example, a transparent insect containing yellow eggs; in the ordinary way of photographing, the eggs would come out dark, but with a yellow screen the eggs would come out full of detail.
The illustrations have been, for the most part, taken on 12 by 10 plates. For this size a comparatively long camera had to be used.
The objectives can be used without any eye-pieces [hyphen present in original, but at a line break], or with varying eye-pieces, according to the magnification required.
Approximate Exposures.
If an object has a normal exposure, say, of 10 seconds when amplified to 20 diameters,
it will require an exposure of 1,000 seconds (just over 16 minutes), if the amplification is to be 200 diameters.
Thus 200/20 = 10
102 = 100
100 x 10 secs. = 1,000 seas.
= 16 mins. +
If the exposure of an object be 1 1/2 mins. when the amplification is 45 diameters, the exposure will be 13 1/2 mins. if the amplification is to be 135 diameters.
452 : 1352 : : 1 1/2 mins. to 13 1/2 mins.
The magnification can be calculated approximately when no eye-piece is used, thus :-
With a 1-inch objective and a 40 inches focus the magnification should be 40 diameters.
Or, with a ith objective and a 30 inches focus the magnification should be 30 x 6 = 180 diameters.
But as the objectives are not always
accurately marked this method is not always reliable.
The photographs from which these illustrations have been taken have been done with achromatic objectives.
In no case has any touching-up been resorted to.
110 DIATOMS
[...]
Next comes the' sun shield, Heliopelta metii (Fig. 3). The illustration is from a photo-micrograph taken under a magnification of 580 diameters [sic; the plate says 350]. No collection of diatoms can be representative without this specimen.
A Water-Mite.
(Mideopsis orbicularis.)
THE tiny Water-mite (Fig. 59) is a new discovery, and has recently been shown at the Quekett Club by Mr. Henry Tavener, the discoverer. It will be sure to interest those who study pond-life. Its body is almost a true circle. Each of the eight legs consists of five segments, the hairs of which point backwards. The object is an exceedingly beautiful one under the microscope.
The original photo-micrograph shows the creature as if amplified to 90 diameters; the focal distance was 75 inches; and the objective used was the 3/4-inch.
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