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The New Acme Stand

From How to See with the Microscope,1880, J.E. Smith, M.D.

During the session of the "Congress" of Microscopists at Indianapolis in 1878, Mr. John W. Sidle, of Philadelphia, and myself formed ourselves into a committee of two for the purpose of devising a new microscope stand.

Mr. Sidle and myself were agreed in our opinions that notwithstanding the recent improvements which of late years had obtained, that there was still room for further effort in the construction of microscopes.

It was then and there proposed, deliberated on, and agreed, that we would unite our energies in the endeavor to construct a microscope stand, which should combine every possible good, be equal to any and all work, exhibiting all the latest appliances, and withal, to combine really reliable workmanship, at the lowest possible cost, in fact at figures no higher than those commanded by inferior instruments. This arrangement contemplated that the author should furnish all the suggestions which his long experience with the microscope might afford, while Mr. Sidle was charged with the mechanical part in the construction of the new stand.

This agreement has been carried out to the letter, and from the date named, until August last, Mr. Sidle and myself have been in close correspondence, and for the purpose named.

The first stand built under our compact was received by me from Mr. Sidle early in August last, and as a matter of course, it got a pretty severe overhauling. Suffice it to say that I became so much pleased with our new bantem, that I gave it the name it bears, and have no hesitancy in recommending this joint production of Mr. Sidle and myself to my friends.

With this preliminary statement. I proceed to give the reader a brief description of our new stand.

The Acme with closed tube, when in the vertical position, is about fourteen inches in heighth, and its weight about five pounds.

The foot is of cast-iron; "horseshoe" shaped and similar to the Hartnack patterns, combining in the smallest compass the necessary weight and accompanying solidity. For real work in the laboratory this form of foot is believed to be superior to all others. For those who prefer the tripod model, Mr. Sidle will furnish this form at the same cost, or in finished brass at an additional cost of $3.50.

The entire instrument is supported by a heavy single pillar of solid brass, the lower portion of which passes through the cast-iron foot, the two parts being held firmly together by a clamp-screw underneath the foot. By virtue of this arrangement, the foot can be detached almost instantly, or, by a half-turn of the lower clamp, the foot can be reversed on the axis of the pi1lar, thus ensuring the greatest stability when the stand is in the horizontal position. The lower shoulder of the brass pillar passing through the foot is accurately turned and fitted, and when desired the moulding at the part of the brass pillar immediately adjacent to the top of the foot can be divided to degrees for the measurement of angular aperture, my own stand is thus arranged.

Besides those already mentioned other advantages occur, from having the foot of the stand removable, some of which may be enumerated as follows:

First, by detaching the base, the instrument can easily be carried in the pocket; it is also much easier to pack, and occupies much less space in the packing. lt can thus be carried from place, to place even in the nar- row accommodations afforded by a small valise, the bother of lugging about the usual microscope case being no longer necessary.

Second, Mr. Sidle provides at a small extra cost a neat black walnut base board, furnished with a small lamp fitted with universal movements. This board has also the necessary brass fittings to receive the pillar of the microscope, which can be clamped to the board. By this arrangement all that is necessary to convert the instrument into a first-class hand microscope is to bring the body to the horizontal position and to adjust the object and the illumnination.

With the stand as thus arranged I have repeatedly exhibited objects illustrative of my lectures to the college class of 150 students, the instrument being passed from hand to hand throughout the entire class, and returned to me everything remaining in perfect order.

To teachers this feature of the stand will be of value. It will also be found a great convenience at times when the microscope is called on to furnish entertainment in the family circle, and objects can thus be exhibited with great rapidity.

By means of a strong trunnion joint the body of the instrument can be inclined at any desired position between the vertical and horizontal, the requisite stability of motion being secured by heavy "cheek-blocks;" the joint has also compensation for wear.

All the working parts of the Acme above the base are of solid brass, bright finished, and nicely lacquered.

The main body-tube is one and five-sixteenth inches in diameter. This tube articulates with the limb by means of heavy "T" guides or angle pieces; thus securing broad bearing surfaces and also perfect freedom from lateral displacement. Mr. Sidle has put himself to much trouble to perfect this portion of the stand.

The main-tube is five inches in length. This is supplemented with a draw-tube, which can be drawn out to the standard length of ten inches when desired.

The coarse adjustment is by rack and pinion. The rack is well cut and durable, and the movement of the tube by means of operating the large milled heads is exceedingly smooth and entirely without "lost motion."

The fine adjustment is by a large milled head placed at the rear of the limnb, and operating the main tube. This milled head is one and one-fourth inches in diameter, and is divided into twenty divisions. It acts directly, i. e., without lever, on a micrometer screw cut fifty threads to the inch, each division of the milled head representing one one-thousandth of an inch. The fine adjustment can therefore be easily made to answer the purpose of a micrometer for measuring small intervals, or for the measurement of cover glasses, etc. In this adjustment the same security against lateral displacement is provided for by means of the "T" angle- pieces, as applied to the rack and pinion movement.

The lower end of main tube carries a nose-piece fitted with the "society screw." This piece can, however, be detached so that the broad guage objectives now in process of construction can be used on this instrument.

The main stage consists of a circular metal plate, three and one-quarter inches in diameter, firmly bolted to the heel of the limb, and in such a manner as to be isolated from the movements of the sub-stage apparatus; four holes are drilled through the main stage plate, and so arranged that the spring clips may be adjusted to hold the object-slide in either a vertical or horizontal position. The spring clips may also be transferred to the under surface of the stage, holding the object slide in contact therewith, when very oblique illumination is to be employed. The well-hole is of the usual size and is provided with a standard screw-thread, by means of which the Woodward prism and other accessory pieces can be readily placed in position. The stand is thus fitted for such emnergencies as required a fixed and central sub-stage, separate from the movements of the mirror; the polariscope is also nicely provided for.

Note. It has lately come to the surface that the diameter ot the "Society screw" is not sufficiently large to meet the requirements of the optician when low powers of the widest apertures are demanded. Mr. Sidle is now making for the author a one-Inch glass having a diameter of over one inch and the Acme has been designed to meet such requirements.

The main stage has also conveniences for centering. Furthermore, a solid plug is furnished which screws into the well-hole, and forming when desired, a solid stage. This plug has an "X" engraved thereon for centering purposes. The sub-stage proper, as well as the concave mirror, are attached to a swinging bar by dove-tailed blocks, The slides having compensation for wear, the sub-stage can be centered. It is one and one-half inches in diam eter and is fitted to carry any of the accessory pieces usually accompanying a first-class outfit. The substage and the mirror both slide with easy friction on the swinging bar.

The swing-bar traverses the face of a circle of brass placed at the rear of the stage, the centre of this circle being in the plane of an object placed on the stage; the centre of this circular plate is solid, that is to say, it presents a solid core of about one inch diameter; outside of this an angular groove is cut therein, in which swings the heel of the swing bar, the method of attachment of the swing bar to the circular plate giving great solidity as well as firmness in motion. Thus it will be seen that the swinger swings not on a centre but around a centre. This part of the mechanism needs only to be seen to be appreciated.

The mirror is of course removable, and a toy candleholder is provided to take its place for the measurement of apertures.

A supplemental circular and revolving stage plate is also furnished, which "slips" on and off instantly as may be required. And by virtue of a nice little contrivance of Mr. Sidle's, the rotatory movement is very smooth and nearly as central as would be expected from stands of much higher cost.

When desired, Messrs. Sidle and Poulk furnish a mechanical stage which slips on and off in place of the rotary plate above mentioned; this mechanical stage has vertical or horizontal motions to the extent ot three-fourths of an inch. This, however, involves an extra cost of $14.

John Sidle other microscope makers

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