CONTRIBUTIONS TO MICRO-MINERALOGY CONTRIBUTIONS TO … · VOL. IV u. 278 CONTRIBUTIONS TO...

CONTRIBUTIONS TO MICRO-MINERALOGY. 277

CONTRIBUTIONS TO MICRO-MINERALOGY. By SAMUEL

HIGHLEY, F.G.S., F.C.S., &c.

PART I.—Instruments of Micro-Mineralogical Research.

FOR the preliminary inquiry as to the general features of amineral mass, I arranged an instrument that should allow ofits free movement in all directions, and that might be left inany position during a prolonged or interrupted examinationby means of the ordinary hand or pocket lens; this is deli-neated in fig. 1, by which its construction will be readilyunderstood. To a firm base a ball-and-socket motion isattached ; from the upper part of the ball arises a circularstem on which fit three right-angled arms, capable of rotatinground their axis to any position, and then being clamped by abroad circular stage that screws on to the axial stem ; throughthe top of each arm a square rod passes, likewise capable ofbeing clamped at any point by little nuts; on the end of eachrotates a disc, studded with three pins, which may be usednaked or clothed with corks, according to the nature of the

Fig. 1.

body under examination: a telescopic universal movement-stand for the lenses completes this arrangement. The stop-

VOL. IV. u

278 CONTRIBUTIONS TO MICRO-MINERALOGY.

plate of the lenses may be conveniently fitted with a smallmoveable Tourmaline analizer. A stouter stand and stem,carrying a Leeson's or Schmidt's goniometer, may be used inplace of the lens, for measuring the angles of large crystals.

Fig. 2.

As a Laboratory Microscope is subject to rough usage, aneconomical form is certainly desirable; the instrument, fig. 2,I contrived to this end. It is of a good size, substantial andneat-looking, has a rack-work movement to the body, bulls-eye condenser, with universal movement, and packs into acase 8 inches by 6£ and 2f inches deep; the whole beingpurchaseable under three pounds. When the drawer is in thecase, the instrument is upright I have adopted a novel modeof bringing it into the inclined position in the cheapest way,by cutting the sides of the box away to a convenient angle, sothat, when the drawer is removed, half of the top of the box,being hinged, falls to the incline, as shown in fig. 2.

For convenience in prosecuting the inquiries here laiddown, I deemed it necessary to construct an instrument that

CONTRIBUTIONS TO MICRO-MINEKALOGY. 279

should be applicable, not merely to microscopical, but tochemical and physical examinations, and that should combinein one, the principles of Nachet's Chemical Microscope withthose of Soleil's Polaroscopes for the measurements of theoptic axes, circular polarization and saccharimetry, Daiker'sSelenite stage, KobelFs Stauroscope, Leeson's and Wollaston'sgoniometers, Jackson's micrometer, with the means of deter-mining the Indices of Refraction in minute crystals, &c.

The instruments known as Nachet's Chemical Microscopesince the Exhibition of 1851, and figured in the editionof Professor Quekett's Treatise of that year, has beenclaimed by Professor J . Lawrence Smith, of the Universityof Louisiana, U. S., as his invention, who seems wrath with 'M. Nachet for not having mentioned his name in connectionwith the instrument, and with Professor Quekett for notknowing, what I believe few others knew till the appearanceof his article in the September number of Silliman's Journalfor 1852, wherein he states that this form of instrumenthe invented in 1850, and brought under the notice of theSociMe de Biologic, of Paris, in the month of September ofthat year, and with improvements in the micro-metrical partsbefore the American Scientific Association in 1851. Thosewho are acquainted with the wholesale way in which the MS.descriptions of Exhibitors' articles were, in most cases as amatter of necessity, cut down to occupy the least possiblespace in the Official Catalogue of the Great Exhibition, willnot, perhaps, think M. Nachet the one to blame that Pro-fessor J . L. Smith's name did not appear in connectionwith the single line* that records the appearance of this Micro-scope at the World's Fair. .Or can Professor Quekett befairly blamed, if with many calls upon his time, he does notread every foreign journal that may issue from the prolificContinental press, or that he did not become acquainted withthe proceedings of the American Scientific Association for1851, before he issued his edition of December in that year,considering that, like our own British Association, it doesnot publish its Reports immediately after its adjournment; orthat he should not have known that Messrs. Wartz and Verdielhad that form of instrument in use at their laboratory inParis, especially as Professor Smith states that only mentionwas made in the Minutes of the Societies referred to, and thatno published account of. his principle had been given to theworld.

Curiously enough I first became acquainted with this prin-

* See Descriptive Catalogue, vol. iii., p. 1242, No. 1370; also Juries'Reports, p. 267.

u 2


ciple of Microscope in 1850 through Dr. Leeson, who,during the summer months of that year, had his large Micro-scope altered by Messrs. Smith and Beck to the form claimedby Professor Smith, for the purpose of prosecuting, during thewinter months, some micro-crystallographical researches ; and

Fig. 3.

on lately referring to Messrs. Smith and Beck's, their account-books showed that the altered instrument had been delivered onOctober 2hth, 1850. On the same day that it was sent home, Irecollect that I went down to Greenwich with Dr. Leeson


to try it, and it answered its purpose admirably ; thus twopersons were working out the same principle at the samemoment (as has frequently happened before in the records ofScience) quite independently of each other; and I think Dr.Leeson* can as fairly claim this form of Microscope forEngland as Professor J . L. Smith may for America.

The principle of introducing reflecting prisms into theconstruction of" the Microscope was, I believe, first employedby Chevalier of Paris, who used a triangular prism in thebody, over his lenses, these being attached at right angles tothe body and pointed down to the stage ; here, however, theprism was a more than useless intervention, the prism onlybeing justified (on account of loss of a small portion of light)when the object-glass is to be placed under the object, as incases where vapours would arise, and thus dim or attacklenses placed over them ; this specially obtains when chemicalsolutions are to be examined, and where heat must be em-ployed. If, however, Chevalier, by a modification of hisarrangement, used, as I believe he did (though I have neverseen his instrument), the lenses under the object, then THEPRINCIPLE is due to him ; the advantageous modification of theangle at which the body is placed, and the resulting positionof the stage, to Professor Smith and Dr. Leeson; the econo-mical adaptation of Soleil's and other instruments, and thegeneral improvement in the arrangement and adjustments tomyself.

In the beginning of 1851 I sent a coloured drawing of theinstrument as I required it modified, and as represented infig. 3, to M. Nachet, who, however, from press of business,could not get it made for me as quickly as I wanted, and Iafterwards got it executed in this country; Kobell's Stauro-scope I have, of course, added since.

The instrument Professor Smith calls THE INVEHTED M I -CROSCOPE, I, in its modified form and from its more generalapplication to crystallological researches, call THE MINEUA-LOGFCAL MICROSCOPE, which I shall now proceed to describe.

The instrument is shown in fig. 3, as arranged for ordinarystructural observations, whilst in fig. 4 it is represented insection, arranged for the optical characters of mineral bodies.

The Base—on a central pivot, screwed into a solid circularbase, rotates a plate that carries the body, prism-box P, object-glass and fine adjustment A ; to the side of the base is firmlyattached a square bar G, that carries the principal stage with

* Dr. Leeson lias never described this, or laid any claim to the inven-tion as yet.


its coarse rackwork adjustment R, and the secondary stage, onto which fits the diaphragm, polarizer, selenite plates, &c. Atube screws into the top of the bar G, on which slides the mir-ror. The object-glass and stages are centered, but the mirrorhas free motion round the supporting-rod.

Fig. 4.

The Body slides into a socket attached to the prism-box atthe proper angle, so that its axis shall be perpendicular to theouter face of the prism P. Within the draw-tube there arefittings to receive glass tubes for examining with a Leeson'sgoniometer and minute-stop, the amount of rotation in liquidsthat exhibit Circular Polarization. If in place of the long body,a tube of iron, round which copper wire has been wound, beused, and the ends of the wires be connected with 12 ormore cells of a Groves or Maynooth battery, the rotation of apolarized ray may be effected.


A shorter body for other optical examinations replaces theordinary one ; this is fitted with a Tourmaline T, a cell for aplate of calc spar C, [cut at right angles to the principal axisof the llhombohedron or Hexagonal Prism,] when the instru-ment is to be used as a modification of Professor Kobell's Stau-roscope for determining Crystal-Systems ; and two lenses L L,with a Jackson's Micrometer M, at the point of their foci, whenrequired for the determination of the optic axes on the principleof Soleil's Instrument.

The Prisin v, is contained in a solid brass box, on the uppersurface of which is screwed the tubes that carry the object-glass ;and one side is removable to allow of the prism being readilytaken out and cleaned.

The prism itself is six-sided, and has four polished faces withangles of such dimensions, that a ray of light reflected down theaxis of the object-glass suffers two internal total reflections, thesecond being axial to the body of the Microscope. The anglesand quality of the glass are points of the greatest importance inthe construction of this instrument, as also are the proper adap-tations of the object-glass and body to the line of reflection.

ANGLES. J. L. SMTH.Upper obtuse = 145°.

„ acute = 55°.Lower obtuse = 107£°.

„ acute = 52£°.

The Fine Adjustment consists of a tube screwed into thetop of the prism-box at right angles to its surface ; over this,tightly, but smoothly, slides another tube on which the object-glasses are screwed. This is kept up to its work by a spring ofcoiled wire, on which it rests; at right angles to its base anarm projects, through which the fine-wormed screw of themilled-head adjuster A works. The spindle of the adjuster A,rotates in a socket projecting from the prism-box.

who siage differs materially in its construction from that ofProfessor Smith's or Nachet's, and allows a far wider scope forpursuing the physical examination of mineral bodies. A stoutsemi-circular arm works up and down the upright bar G, bymeans of a rack and pinion R. This supports a circular stageS, figs. 4 and 5 ; two axes at the circumference of the stagepass through the extremities of the arm; the stage beingkept in a horizontal position by means of the nut w, whichpasses through the arm into the stage; the nuts, N, screwingon to the axes, clamp the stage firmly to the arm. The stagehas a projecting ring, within which a graduated plate rotateswhen certain optical examinations have to be made, but which


is ordinarily fitted with a plain metal plate that rises flush withthe top of the axes of the stage, or this may be replaced withanother plate, which rests on three screws, and has an arm pro-jecting from one side, by which heat may be communicated tothe centre of the stage, when a spirit-lamp is placed under it;the three points of support not allowing the heat to be com-municated to the other metal work. These three plates haveapertures in their centres, with screw rings, so that they may befitted with circles of thin glass, when liquids are used. If amovement is required beyond that afforded by the object slideshaving free play in all directions, a circular plate of metal orglass, about I inch less in diameter than the bottom plate of thestage, with an inch aperture in the centre, may be used as sug-gested by Professor Smith, motion being imparted by the ope-rator's fingers, or a Tilley's, or any other form of mechanicalmovement may be fitted within the ring of the stage. Of course,in this instrument the object has to be placed with the thincover downwards.

Fig. 5.

By removing the nut N, the stage has free movementon its axes, and may be inclined to any angle, as is shown infig. 4, S. S. One axe is longer than the other, and is soarranged that the graduated circle before mentioned may rotateon it, and be clamped, when desired, by the nut N. An index-


point I, fig. 4, rises from the stage arm as the starting-point forthe readings. Thus, in measuring the optic axes of a crystal,the stage is inclined till one optic axe is properly cut by themicrometic lines M, in the short body; the graduated circlerotated till zero stands opposite the index-point I, and is thereclamped; the stage is again inclined till the second axe cutsthe micrometic lines, and as the graduated circle has passed onwith the stage, the readings are taken from the fixed index-point I. This circle is graduated from 1 to 180 on each half,so that the reading may be taken on whichever side the stagemay be inclined. Its use as a Wollaston goniometer, and otheroperations for which this is adapted, will be given under theproper heads of these COTTKIBTJTIONS. The graduated circlealso fits over an eye-piece containing a double-image prism, andthus constitutes a Leeson's goniometer. The manipulationand details of construction will be given under the head of" Goniometry." It will thus be seen that one graduated circleeconomically does the work of three by this arrangement

The Secondary stage requires no special description, as theordinary accessory instruments are mounted so as to slip on aring that rises from its surface. I find a reflecting bundle ofthin glass the best Polarizer for this form of Microscope; byremoving the back and using the plain mirror, it may also beused as a Refracting Polarizer. An electro-magnet arrangedso that its poles, which terminate in small sliding cones, may bebrought into the field of view without intercepting much of thelight reflected from the mirror, is mounted on a fitting, so thatwhen required it slips on the square bar G, between the princi-pal and secondary stage.

It will be readily seen that this form of microscope possessesgreat advantages for chemical and mineralogical investigations,as the stage is in a far better position for the eye to watch themanipulations than in the ordinary instruments; and the object-glass being under the object cannot be dimmed or attacked bythe vapours arising from the liquids under examination. Infact, Professor Bailey uses hydro-fluoric acid to determinewhether markings on a siliceous body are to be regarded aselevations or depressions, as those parts that are elevated willbe last seen under the dissolving action of the acid. ProfessorRiddell, in a note to Professor Smith, states, that after twelvemonths' trial he will not willingly return to the habitual use ofany known form of microscope, " especially with high powers."

Moreover, as the plate that carries the body and object-glassrotates on the base, when the parts are properly centred, thismay be used as a Demonstrating Microscope, as the body can


be rotated to two persons on each side of the demonstratorafter he lias arranged the object, and thus be examined by fivepersons in succession. This has the advantage of economy overNachel's three and four bodied microscopes (see vol. ii., page 72),even if some of its other points are not attained.

Kc-ngent Botiics.—In vol. ii., page 58, of this Journal, myfriend Dr. Beale described and figured a Re-agent Drop-bottle used by him, and an improvement on its form by myself,

•p- 6 Finding that many persons meet with a diffi-~~— culty in filling them by the plan there recom-

mended, though it is a very simple operation,and moreover, that certain re-agents aredecomposed when they enter the heatedbottle, I have again improved iis construc-tion, which will be readily understood byfig. 6. Instead of drawing out the neck ofthe bottle to a Gapillary-tube, a piece ofthermometer-tube is drawn out to a finepoint, and is then ground into the neck ofthe bottle like a stopper; on the outsideof the neck a glass cap is ground in the sameway as in a spirit-lamp. When the bottlehas to be filled, the drop-tube stopper isremoved, and firmly replaced after the bottleis about two thirds full, the warmth of thehand affecting the contained air that rises tothe end of the bottle when the drop-tube is

pointed downwards on a slide, forces the liquor through thethermometer-tube stopper drop by drop; and this is moresatisfactorily effected, as the bore is of one diameter along itswhole length, instead of being an elongated cone as in the oldform. There should be a sufficient quantity. of these in aproper case; such, with the other instruments here described,may be obtained of Messrs. Murray and Heath, opticians, of43 Piccadilly. Watch-glasses, excavated and plain slides, stir-rers, a Sinee's battery for electro-chemical decompositions, andsi. Groves' battery for examining the effects of electro-magneticcurrents on crystallization, &c, will complete the micro-mineralo-gical laboratory, which may equal, if not rival, Wollaston'slaboratory that was contained in a tea-tray.

CONTRIBUTIONS TO MICRO-MINERALOGY CONTRIBUTIONS TO … · VOL. IV u. 278 CONTRIBUTIONS TO...

Documents

Transcript of CONTRIBUTIONS TO MICRO-MINERALOGY CONTRIBUTIONS TO … · VOL. IV u. 278 CONTRIBUTIONS TO...