12-2 



HARDWICKE'S SCIENCE-GOSSIP. 



microscopic wonders are continued, and the author ' 

 gives us four figures of infusorial animalcules. One 

 of these represents a remarkable instance of evolu- 

 tion, and, no doubt, if Darwin had only come across 

 a similar instance, he would have traced man to this 

 animalcule, rather than to a larva form of an 

 ascidian. (See fig. 64, on page 124.) 



In addition to the copy of the figure, we give 

 the discoverer's description of it : — "But of all the 

 objects, that represented by figure 5 is the most 

 bizarre ; it was found in an infusion of the royal 

 anemony, in common water, kept eight days; 'he whole 

 body is covered with a mark representing an human 

 face, with six radii or claws, and a tail crowned at 

 top with a kind of heart. Its motion was but dull, 

 yet sufficient to show, beyond all doubt, that it was 

 of the animalcular kind." 



About this time, Mr. Henry Baker, E.R.S., 

 F.S.A.,' published the result of his microscopic in- 

 vestigations. These observations were made with 

 an instrument constructed for him by Mr. Cutf, and 

 of which he speaks very highly. Having once 

 possessed one of these microscopes, we can speak 

 favourably of the mechanical part'of it ; the lenses 

 were double-convex, and probably neither better 

 nor worse than those made by other opticians years 

 before. The subsidiary apparatus weer perhaps more 

 numerous than usual. In the year 1747 Mr. Cuff 

 invented an eye-piece micrometer, of which a de- 

 tailed account was given by the first President 

 (under the Royal Charter) of the Royal Society, 

 Martin Folkes, Esq.* 



" This Micrometer only consists of a Lattice of 

 fine Silver Wire, distant from each other one-fiftieth 

 of an inch, intersecting at right Angles and so 

 placed in the focus of the Eye Glass as to divide 

 the whole visible Area of the Microscope into 

 Squares, whose Sides are each ^ of an Inch." 



The plan adopted to ascertain the true magnitude 

 of an object was similar to that now used when 

 the modern eye-piece micrometer is employed; 

 instead, however, of a stage micrometer, the 

 diagonal scale was used, and when this was not 

 practicable, a minute object was measured under 

 a low power, and this was again employed as a unit 

 of measure for the higher power. 



The usual number of objectives sold with the 

 instrument was six, the following table shows their 

 magnifying powers : — 



No. 1. 189 diameters. 



2. 161 „ 



3. 84 „ 



4. 49 



5. 28 



6. 17i 



* This gentleman presided eleven years at the meetings of 

 the Society, and would have probably been elected for the 

 twelfth time had not paralysis compelled him to decline the 

 honour. 



Mr. Baker had, he tells us, an extra lens made 

 particularly for him, and which had the extraor- 

 dinary magnifying power of 320 diameters. 



Our No. 1 was so dark, as to be virtually useless ; 

 what the above glass was, it is difficult to imagine. 

 The diameter of the lens in No. 1 was about the 

 eighth of an inch ; this was dropped into a little 

 brass cell, with an aperture of not more than the ^V 

 of an inch; this was the only means then known of 

 counteracting the chromatic and spherical aber- 

 rations of single lenses. The microscope seems to 

 have been a popular scientific instrument in the 

 middle and latter part of the last century, if we 

 may judge by the demand for works relating thereto. 

 Baker published three editions of the " Microscope 

 made Easy," and only one year elapsed between the 

 publication of the second and third editions. This 

 work was also translated into French, German, and 

 Dutch. In 1753, nine years after the publication 

 of the third edition of the "Microscope made 

 Easy," appeared the first edition of his "Employ- 

 ment for the Microscope," Svo., pp. 466, plates 17; 

 a second edition was published with an additional 

 plate in 1764. In 1785 the two works just named 

 were published, under the title " Of Microscopes, 

 and the Discoveries made thereby." Vol. I. "The 

 Microscope made Easy," 8vo., pp. 324, plates 15. 

 Vol. II. "Employment for the Microscope," 

 pp. 452, plates 15. Baker also published "An 

 Attempt towards a Natural History of the Polype," 

 Svo., pp. 222, plate 1, and also illustrated with 

 woodcuts : London, 1743. This was translated into 

 French under the title of an " Essai sur l'Histoire 

 naturelle du Polype Insecte, traduit de l'Anglois 

 par P. Dumours," Svo., pp. 359, plates 22, Paris, 

 1744. It seems that M. Dumours "bearbeitet" (as 

 the Germans would say) as well as translated Baker's 

 work. "Trembley'sMemoires pour servir a l'Histoire 

 d'un genre de Polypes d'eau douce," did not appear 

 until 1744. 



In the "Employment for the Microscope" are 

 given directions for the preparation of objects for 

 the microscope. The title-page gives a good idea 

 of the character of the work. The following is a 

 copy of that appended to the 2nd edition : — 



"EMPLOYMENT 



FOR THE 



MICROSCOPE. 



In TWO PARTS. 



I. Au Examination of Salts and Saline Sub- 

 stances, their amazing Configurations and Crystals as 

 formed under the eye of the Observer, 



WITH 



Plain directions how to prepare such Substances 

 and preserve them in constant Readiness for In- 

 spection, whereby the Curious may always be fur- 



