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SUPPLEMENT 



covering one another like the tiling of a house, 

 are interesting facts ascertained by microscopic 

 observation. 



Many of the improvements recently intro- 

 duced into the elements of the microscope, are 

 the results of elaborate inquiries respecting 

 the scales on the wings of butterflies, whence 

 the latter have come to be denominated test 

 objects, as being peculiarly fitted to test or 

 prove the defining and penetrating power of 

 the best instruments. The information in 

 consequence derived concerning these delicate 

 formations, may be regarded by some as more 

 curious than useful; it is at least curious, and 

 we believe few persons will deem it beneath 

 the dignity of science to investigate the min- 

 utest atom, since it could be produced only by 

 the same plastic energy that evoked the universe 

 into being. Dr Goring has the merit of being 

 the first to examine into all the details of these 

 objects, which he has developed with much 

 success, though principally with a view to 

 suggest those important improvements in the 

 microscope, which have since been reduced to 

 practice by his talented coadjutor, Mr Pritchard, 

 Avho by his various writings and optical con- 

 structions, has at once stamped himself a 

 philosopher, and if not the first, one of the first 

 practical opticians of the day. 



Leeuwenhoeck remarks, when speaking of 

 the scales on the wings of butterflies, u that 

 if an hundred, or more, of them were to be 

 seen lying together, each would appear of a 

 different shape." Now, though this observa- 

 tion is strictly true, inasmuch as there is the 

 same variety exhibited in the formation of 

 these atoms as in that of the human counte- 

 nance, still this is not the grand point of admi- 

 ration : the most wonderful fact connected with 

 them is, that amidst all the variety of indi- 

 viduals, we no more mistake the different spe- 

 cies of these scales, than we do the various 

 species of the human race, in consequence of 

 the great variety of features observable in 

 them. Since these objects have been subjec- 

 ted to severe examination, questions have arisen 

 regarding the real nature of their structure, 

 which have perhaps been disputed beyond the 

 point of usefulness. In describing the varie 

 ties which are offered in our illustrations, we 

 shall take occasion to remark upon the various 

 opinions that are entertained respecting the 

 striated markings on these scales. It may be 

 necessary to inform the general reader that 

 these minute atoms form that impalpable pow- 

 der on the wing of a butterfly, which clings 

 1o the finger whenever we touch the insect. 



We proceed to describe in order figs. 10 to 

 21 inclusive, in plate 34. The objects are all 

 shown under a superficial magnifying power 

 o f 9 00 . F i g 1 0. Scale of th e red under -wing 

 buttr.rjiy This is an exceedingly beautiful 



formation, under a deep power of the micro- 

 scope. The longitudinal and cross striae (or 

 markings) are easily developed by a good de- 

 fining power. The cross lines give to the 

 others the appearance of strings of beads. It 

 is asserted that this apparent structure in the 

 object under review, and in others of this class, 

 is really the interlocking of the serrated 

 edges of the fibres composing the scale. The 

 opinion is founded on a presumed analogy be- 

 tween these formations and the laminse in the 

 crystalline lenses of fishes, &c. We are, how- 

 ever, inclined to dispute this opinion, since 

 there is no general resemblance between 

 the structures to justify the argument from 

 analogy in this case ; and moreover, a less 

 overstrained analogy may be inferred between 

 different, objects of this class, some of which 

 present their details to view, under a powerful 

 magnifier in a manner that dispels all doubt 

 as to their real nature. Of these we shall 

 speak in order ; simply observing in this place, 

 that from an attentive examination of various 

 scales, and their probable similarity of struc- 

 ture, we are led to think that, in the formation 

 before us, the longitudinal striae are fibres, pro- 

 duced on the same principle as the hairs of 

 animals, and consist of a number of minute 

 cups growing out of each other ; and that the 

 cross strise are merely indications of the seve- 

 ral insertions. The fibres are connected by a 

 delicate tissue. 



Figs. 11, 12, and 13. Scales of the brassica 

 butterfly. These are three varieties of scales 

 from the wings of the brassica, or cabbage 

 butterfly. Fig. 11. resembles the object pre- 

 viously described, excepting that there is a 

 marked and decisive difference between the 

 contour of the two scales. Fig. 13. is termed 

 the Brassica curiosa ; and is no less remarkable 

 for its exterior form, than for the singular dis- 

 position of the striae on its surface. Fig. 13. is 

 a scale from the pieris brassica^ and we shall 

 connect our remarks upon this object with fig. 

 17, the scale of the podura plumbea, as these 

 two delicate formations are the severest tests of 

 microscopic definition and penetration, and the 

 examination of them has led to a lengthened con- 

 troversy regarding the true character of the 

 lines that cover them. In our illustrations, 

 the delicate longitudinal striae only are shown ; 

 but under a suitable power, and with a due 

 management of the light, these objects exhibit 

 diagonal lines whose real nature, owing to 

 their extreme fineness, can merely be inferred 

 from assumed analogies. The scales ot the 

 lepisma saccharina offer their details to the 

 eye in a very satisfactory manner, under a linear 

 power of 200 or 300 ; and we are convinced 

 that they afford the best explanation that can 

 be obtained regarding the podura and brassi- 

 ca. The lepisma distinctly shows a series ol 



