ON MICROSCOPIC DISCOVERY. 



591 



dichroite, serve to polarize the light passing 

 through it, and to make it visible. 



" A few other similar experiments may be 

 mentioned : 



" I. Add sulphuric acid to common salt, or 

 muriate of soda, or to carbonate of ammonia. 



" 2. Add sulphuric acid to bichromate of pot- 

 ass or muriate of soda. The result is crystals 

 of sulphate of soda, with chloro-chromic acid. 



" 3. Add acetic acid to the bichromate of pot- 

 ass. The crystallization of the bichromate 

 takes place in very beautiful forms, 



" 4. Add sulphate of alumina and potass to 

 muriate of cobalt. The crystals of the alum 

 form in great perfection. 



"5. Add acetic acid to nitrate of copper. The 

 biperacetate of copper forms slowly and crystal- 

 lizes in great beauty. 



" 6. Add terrocyanate of potass to sulphate 

 of iron. 



" 7. Add nitrate of potass, or aqua potassze, to 

 sulphuric acid. The sulphate of potass forms 

 in solution. Raise the upper glass with a 

 knife the smallest degree, and let it fall again ; 

 the crystallization is instant. 



" 8. The smallest drop of any liquid contain- 

 ing lead may be examined by the usual tests 

 for lead ; and wine may, in the same way, be 

 tested in a drop not bigger than a pin's point. 



"9. The ben-iodide of mercury is a beautiful 

 crystal, and open to a variety of experiments. 



" 10. Investigate the comparative purity of 

 successive crystallizations of nitrate of potass." 1 



In proceeding to consider the formation of 

 minute mineral bodies, our attention is called, 

 in the first place, to what are designated the 

 active molecules of matter. With the excep- 

 tion of bodies perfectly soluble in water, 

 metals that cannot be reduced to atoms suf- 

 ficiently minute, and a few other substances, 

 the whole range of matter exhibits the phe- 

 nomena of molecular activity. The method of 

 bringing these atoms under microscopic in- 

 vestigation is very simple. On a slip of glass, 

 adapted to the stage of the microscope, place 

 a small drop of water ; then with any sub- 

 stance sufficiently hard, rub the mineral body 

 whose atoms you require; touch the water 

 with the rubber, and it will transfer to the 

 fluid the minute particles separated by friction. 

 Apply a deep power, say a one-twentieth inch 

 doublet, and a vast number of apparently small 

 spheres will be seen in rapid and continual 

 motion. This motion of the particles will not 

 cease in any definite time, if care be taken to 

 supply fresh water as the other evaporates. 

 The movement of these atoms very closely re- 

 sembles that of the infusorial monads and the 

 spermatic animalcules. The writer was led 

 himself to experiment on the nature of these 



1 Gould's Companion to the Microscope, p. 62, et seq. 



active molecules, and from a variety of phe- 

 nomena presented by minute particles of cam- 

 phor floating in spirits of turpentine, he was 

 led to attribute the activity to electric or mag- 

 netic agency. Having put a drop of spirits 

 of turpentine on a slip of glass, he added 

 thereto an extremely thin shaving of camphor, 

 which was rapidly decomposed by the spirit, 

 and fell down into minute crystals, spheres, 

 cylinders, circular planes, &c. The activity 

 of these tiny forms was truly wonderful and 

 delightful to witness ; and though this is not 

 the great point to which he would now direct 

 attention, he still thinks that a detailed ac- 

 count of the appearances will be interesting 

 to all who have not made similar observations. 

 The crystals were rhomboidal, and frequently 

 revolved with greater or less rapidity on their 

 longest axis; after turning one way for some 

 time, they would then reverse their motion ; 

 at other times, the revolving movement would 

 be entirely suspended, and they would direct 

 alternately the two ends (poles?) of their axis 

 to some particular point in the field. The 

 spheres exhibited the same phenomena in re- 

 volving, with this peculiarity, that the rapidity 

 of their motion far exceeded that of the crystals ; 

 and whenever they ceased to revolve, it was 

 to fly off in a right line to another quarter of 

 the field. It should be remarked that whilst 

 revolving, neither the crystals nor the spheres 

 made any progressive advance, at least speak- 

 ing generally. The circular planes revolved 

 in like manner on a diametric axis ; and these 

 progressed over the field in the direction of the 

 revolution. The small cylindric forms pointed 

 their ends alternately to the same point, fre- 

 quently revolved on their axes, and occasion- 

 ally exhibited all the lively motions of the 

 most active vibrio animalcules. When the 

 crystallizing process began, as the turpentine 

 evaporated round the edges of the field, these 

 several forms cleared from the centre and 

 united themselves to the foliations. It was 

 then that a vast number of very minute par- 

 ticles were discovered, moving rapidly in the 

 manner of ordinary molecular atoms ; as the 

 star-shaped crystals began to form in the 

 midst of them, they were^seen to strike rapidly 

 and repeatedly against the projecting points, 

 till at length they adhered to the mass, and 

 were incorporated with it. The phenomenon 

 was precisely that of an insulated cork ball 

 striking against the conductor of an electrical 

 machine, in which case it becomes electrified 

 itself and is repelled, when quickly losing the 

 electricity it had acquired, it again strikes the 

 conductor. It seems probable then that mole- 

 cular activity is the mere result of successive 

 attraction and repulsion among a vast number 

 of suspended particles ; and it does not appear 

 difficult to conceive that motion will be- 



