86 



SCIENCE-GOSSIP. 



tree-life of such loveliness as Rembrandt, prince 

 of etchers, would have failed to imitate. 



The accompanying drawing illustrates specimens 

 of dendritic crystals, figs, i and 3 being natural 

 size. Fig. 2 is an enlargement, drawn from a 

 micro-photograph of fig. 1, kindly taken by Captain 

 Barnes. The black mark shown in the magnified 

 example appears to be the origin of this beautiful 

 pattern. 



The dendritic crystal is formed by chemical 

 action set up by the accidental deposition of a 

 minute fragment of copper upon the surface of 

 paper during the processes of manufacture or of 

 printing : the presence of the minute fragments 

 of copper deposited being probably due to the 

 wear and tear of the paper-making or the printing 

 machinery, so far as the mechanism is built up of 

 copper. The agency of manganese and the action 

 of heat or of moisture in building up the dendritic 

 crystal, tracing its arborescent characters black 

 upon white on the surface, as well as in the very 

 substance of the paper, must be left for a future 

 article. 



Unlike crystals from saline and other solutions, 

 which may be rapidly formed upon the stage of the 

 microscope " while you wait " as the signboard 

 hath it, the dendritic crystal requires, as far as I 

 have observed, rather more than twenty years 

 before reaching its fullest development. 



However, just as there is a firm in Chelsea who 

 have been wresting from nature one of the most 

 hidden of her geological secrets, by transmuting a 

 block of chalk into a block of marble in a few 

 hours, it is amongst the possibilities of the near 

 future that dendritic crystals may quickly be pro- 

 duced in the laboratory, rivalling, perhaps excelling, 

 the specimens hitherto known. 



I have never as yet seen a specimen in a book 

 older than 1835, or younger than 1882. In the 

 latter case, all the examples of the crystals were 

 small in size, and their arborescent character was 

 not nearly so well defined and luxuriant as in the 

 volume aged three-score years. 



It would be interesting to learn the experience 

 of brother microscopists, and I would be glad 

 to see reports in Science-Gossip from those 

 whose experience differs from mine on the 

 point. 



A somewhat remarkable fact touching this sub- 

 ject is that although I have examined scores of 

 volumes of foreign origin I have never yet been 

 rewarded by the discovery of a single specimen. 

 Never having seen an American or continental 

 paper-making or printing machine, I know not 

 whether the absence of crystals is due to there 

 being no copper in their mechanism. I can hardly 

 imagine any scheme of winnowing away foreign 

 particles, or of pulp-manipulation that would be so 

 perfect as to wholly banish the tiny granule of 



copper, if any of that metal were in the make of 

 the machine. 



These crystals vary in size ; the smallest are 

 barely visible to the naked eye as, apparently, a 

 minute black dot. A giant specimen would cover 

 a threepenny piece. A good Coddington lens or a 

 two-inch objective is indispensable for examina- 

 tion of the smaller specimens, but much of the 

 beauty of the larger examples is manifest to the 

 unaided eye. With a small lens one may go on a 

 voyage of discovery amongst one's books in quest 

 of crystalline beauty without an}- help from the 

 microscope. Non-crystalline marks are hard 

 in outline and of rigidly defined harshness and. 

 blackness at their edges, whilst the dendritic 

 crystal that looks "blottesque" at half-a-yard's 

 distance is found when closely examined to be 

 fashioned with the utmost delicacy of filigree 

 structure, as if indeed it had been designed in 

 fairyland, and the master-craftsman had made the 

 pattern a blending of the beauty of tree-life with 

 the fantasy of the marine algae. 



34, Woodlands Road, Ilford, Essex ; May, 1S94. 



IMPROVED SPIRIT LEVELS. 



"\ 'X TE have received from Mr. J. J. Hicks, of 

 Hatton Garden, specimens of his new 

 circular spirit levels. So much disappointment 

 has been caused by the almost inevitable failure 

 of circular levels, after a short period of service, 



that we are sure those readers who make use of 

 the camera in their scientific work will welcome 

 this improvement, in which leakage, corrosion, 

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 spirit being enclosed in a blown glass, hermeti- 

 cally sealed, instead of being enclosed by cement, 

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 mounted in brass with screw-holes ready for fixing 

 to the camera, and are produced in various qualities 



and sizes, from eighteen-pence upwards, the more 

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 inside and out. We have tested their sensitiveness 

 when attached to the camera, and are well pleased 

 with their performance ; there are, however, many 

 other purposes for which a trustworthy circular 

 level offers great advantages over the tubular kind- 



