Popular Science Monthly/Volume 8/November 1875/A Home-Made Microscope
By JOHN MICHELS.
THE progress of science in recent times is in a great degree due to the employment of instrumental aids to observation; and whoever wishes to keep up with this advance, or indeed to gain an adequate notion of its extent and interest, can only do so by the use of similar means. In the study of chemistry, experiments and actual observation of the behavior of substances under various conditions, are indispensable; in physics, multifarious appliances for the illustration of principles are constantly required; in astronomy. the telescope is absolutely essential; and, in biology, vast departments can be brought within our reach only by the aid of the microscope. This latter instrument, especially, has a wide range of application. The investigations of the anatomist and physiologist cannot go on without it; the educated physician has it in daily use; the tradesman finds it an important aid in testing the purity of commodities; and the student in many departments of physical science is obliged to use it in his work. When to all these considerations we add that the manipulation of the microscope, for the purpose of ordinary observation, may be acquired without much difficulty, and that the instrument itself may be procured at a moderate cost, we have said enough to justify the assertion that every educated person ought to possess a microscope, even as he possesses a collection of books.
Fig. 1.—Complete Instrument.
To derive advantage from the use of the microscope, it is not necessary that one should master all the technicalities of the instrument, or be possessed of all the improved appliances for extremely minute observations. Professional microscopists have recognized the error of directing all one's efforts on such tasks as the resolution of test-plates, so long as really urgent work remains undone. Thus, the President of the "Quekett Microscopical Society" remarked:
"Our opticians have gone ahead of the observers, they have placed in our hands powerful means of research. I fear the account of the talent committed to our charge will not be one of which we may be proud. I fear we are too apt to pride ourselves as being the possessors of superior instruments; each man pits his instrument in rivalry against his neighbor's, and rejoices that he can beat him in the resolution of Nobert's test-plate."
Mr. Le Neeve Forster, in the above remarks, doubtless strikes at the root of an evil that is fast becoming a nuisance, to the utter detriment of useful and sound work; the test-slide and diatom fever has spread like an infection among all classes of microscopists, and has resulted in an extravagant system of expenditure foreign to true scientific research. I find that $1,650 is now asked for a first-class instrument and fittings, and as much as $40 apiece for diatom-slides.
These eccentricities of leading microscopists appear to have received protests from various quarters, for the President of the Royal Microscopical Society, in his last address, states:
"It has been cast at us, as Fellows of this Society, that we do nothing but improve our tools, or measure the markings on the frustules of a diatom."
One reason for the confessed poverty of microscopical results may be ascribed to the want of sufficient workers to cover so vast a field of research. It is to be regretted that many professional men, whose occupation would seem to demand the daily use of the microscope, deny themselves the facilities it offers. I apprehend that the explanation of this apparent neglect will be found in the high price asked for first-class instruments, and the absence in the market of a good standard instrument that combines the advantages of being of the best workmanship, full-sized, portable in form, and moderate in price.
Messrs. Baker, Crouch, Collins, and especially Swift, all of London, produce such microscopes, but, as their importation doubles the cost, their chief merit of cheapness is lost. In our own country, opticians have proved that they can produce work that cannot be surpassed, provided that their patrons entertain the same views as Sir Charles Surface respecting the expense; but those of more moderate means, who wish to purchase a good working microscope at a moderate cost, are offered a pretentious display of foreign and domestic forms, totally unfit for professional or scientific use. If makers of microscopes would take a lesson from the best telescope-makers, and, instead of multiplying the number of their models, combine their energy in the production of a good standard instrument, filling the conditions that I have already stated, they would promote the cause of science and concentrate their business.
Fig. 2.—Instrument folded for Carriage.
Those who have read the biographical and obituary sketches of eminent microscopists have probably noticed that it was a favorite pursuit with many of them to make their own instruments. In the Monthly Microscopical Journal, for March last, will be found such a notice included in the address of the President of the Royal Microscopical Society, referring to the death of a Fellow, Mr. John Williams, who was also Assistant Secretary of the Royal Astronomical Society. He said:
"He constructed more than one microscope out of odds and ends, which be put together with much skill and ingenuity. His most elaborate microscope was made with cardboard tubes and brass-screw adjustments. This instrument, when supplied with objectives by Ross and others, contrasted favorably, in point of utility, with constructions of a more costly character."
The perusal of this notice, followed by a communication to the effect that in some of the London scientific schools the students are required (when practicable) to make all the apparatus they use, has prompted me to describe a microscope made by myself about six years ago, and which is now but little the worse for wear.
So far as the stand is concerned, it can be easily made at home, at a trifling cost. The materials are of a humble character, but the optical arrangements are full-sized, and of the highest quality. Within the limits of its use this instrument will exhibit objects with much perfection. By a reference to the cuts, it will be observed that many of the parts are cylindrical, and may be turned on any ordinary lathe in a few minutes.
To make a microscope such as I shall now describe, requires little mechanical skill. If my directions are followed, and strict attention given to the drawings, no difficulty will be encountered, but neatness and precision are of course essential First provide a wood rod about 15 inches long, and of the circumference of Fig. 3.
Then take some paper of firm texture, and wind it around the rod three or four times according to its thickness, applying mucilage all the time; immediately withdraw the paper casing, and place on one side to dry. This should form a perfectly true and firm tube. When dry, replace it on the rod, and with a sharp knife cut off from each end sufficient to leave the remainder 7½ inches long.
The other parts are of wood. I suggest mahogany as the most appropriate, and susceptible of the best finish; but any well-seasoned, hard wood will do. To proceed, make a rod, like an ordinary ruler, 13½ inches long, and of the diameter of Fig. 4. Now turn, or get turned, a tube, 4½ inches long, the walls of which shall be ¼ of an inch thick; Fig. 5 will give the diameter.
A part which I call the cradle can now be made; the form is shown in section, at Fig. 6; its length must be 3¾ inches.
The support for the stage requires no special explanation; a full-sized drawing is given at Fig. 7.
The stage itself can be made of wood, but gutta-percha is better,
and, if placed in hot water, it can afterward be easily moulded to the pattern given at Fig. 9.
Smooth the surface while still warm with glass plates, and steady the back with two strips of wood. The shaded part at the lower edge shows a piece of wood fixed thereon to support a zoöphite trough or glass slides. Fig. 10 represents the upper and lower parts of a leg, two of which are required, 9¾ inches long, and the size shown in cut. On the upper portion the brass hinged attachment is fixed.
The appearance of the paper tube, with eye-piece and object-glass in position, can be seen at Fig. 11. The parts which have been already described being completed, proceed to fix them together with glue. Their correct position can be seen at a glance by reference to Fig. 12.
First fix the cradle, 6, upon the rod, 4 within three-quarters of an inch of the end next the tube, 5, upon the cradle, as shown. The stage and support can next be fastened, but first insert the paper tube, Fig. 11, in wooden tube, 5, and measure the most convenient
place to fix the stage, so that the object-glass can approach the object without bringing the tube too low down. A trial will at once fix the proper spot.
The legs are attached by screws to the cradle, as seen in Figs. 1 and 2. The whole being now in form, clean and French-polish.
Also paint the inside of the paper tube a dull black, using drop-black, turpentine, and a little Japan varnish to fix color, and the outside with a mixture of Indian and common inks. Finally, line tube, 5, with a piece of fine cloth. If this is neatly done, the paper tube, Fig. 11, will pass and repass as smoothly as the motion of a telescope, which is controlled in a similar manner.
There is no reason why the optical parts should not be made by the student, but necessary instructions would require a series of articles. Assuming, therefore, that such portions will be purchased, a few words on that head may be necessary.
If only one eye-piece is required, select letter B. Next take tube. Fig. 11, to an optician, and ask him to fit a Royal Microscopical Society screw, Fig. 8, in the centre of a wood block. This block and screw must be fastened into one end of the paper tube, and will carry the object-glass.
The last fitting will be the mirror, a reduced drawing of which is shown at Fig. 13.
The mirror should be at least two inches in diameter, and the ring which passes over the rod. Fig. 4, should be split, and about half an inch in breadth, and, being made somewhat too small, will grip the rod, and be free from unsteady movement.
To hold the slide upon the stage in position, pass two moderate-sized India-rubber bands upon each side, and a third crosswise near the bottom; a very delicate movement can be given to a slide thus held.
In regard to object-glasses I have little to add. Such as I should have specially recommended are not to be obtained in this country; but, to commence operations with, purchase the best 1 inch and ½inch your means will permit. I much regret that the objectives made by Gundlach, of Berlin, are not introduced. It would be a boon to those who cannot afford to purchase the best glasses. I have seen them tested at the Royal Microscopical Society with the most costly objectives, where their performance has elicited the highest praise. When I state that an immersion 1/16 costs in London but £3 10s., the price of the low powers can be calculated.
These 1/16ths have wonderful definition, and can be used upon all slides, having the ordinary thin glass cover, a great advantage. Such a glass could be sold here for thirty dollars, and the 1-inch and ½ inch for about ten dollars apiece. Except for special work, these objectives answer every purpose. The sketch at Fig. 1 is a correct drawing of the complete instrument, in position for use; and at Fig. 2, the same folded, showing its convenience and portability. The whole weighs about a pound, and can be carried, with eye-piece and object-glass ready for use, either in a bag or a light box 14 x 3½ X 3 inches.
Those who possess very large instruments will find this model a most useful addition for occasional use when traveling or demonstrating subjects away from home.
This form of microscope is offered as convenient for beginners, who, unable to purchase a complete instrument, still wish to make a beginning and start upon a right principle. Although a complete microscope can be purchased for about the same amount that the optical portions of this will cost, it will be wanting in the chief essentials of a good working instrument. Diminutive size, smallness of field, poor light, shortness of tube, absence of Society's screw, and other evils, will soon cause it to be cast aside, resulting in the loss of the original outlay; whereas the parts purchased under the above directions are portions of a first-class instrument, obtained in advance, which will never become obsolete.
The immense field of inquiry within the grasp of the microscopist is apt to disconcert and confuse the student. His course, however, should be well defined. First let him familiarize himself with what has been done by others, and then confine his attention strictly to those subjects which have reference to his profession or pursuit. If he has no special occupation, I would advise him to select a particular line of study, and let that be the thread on which to string his subsidiary matter, mounting his own objects, and carefully registering his observations. He will thus slowly but surely accumulate knowledge that will benefit the cause of science.