62 



HARD WICKE ' S 5 CIENCE- G O SSIP. 



Fig. 61. — The Hofmann Camera 

 Lucida. 



an oven for two or three days, the Canada Balsam 

 will then easily chip off with a knife, then wash them 

 in soda water. — S. C. Hinchs. 



New Forms of Camera Lucida. — In the 

 December number of the "Bulletin de la Societe 

 Beige de Microscopie," Dr. Henry van Heurck 

 describes a new form of camera lucida, invented by 

 D. T. Hofmann (29 Rue Bernard, Paris), the well- 

 known optician. This camera lucida not only shows 

 the pencil with great distinctness, but every detail of 

 the image. Every one who uses the camera lucida is 

 annoyed at the uncertainty that accompanies the 

 ordinary apparatus, particularly when it is necessary 

 to reproduce delicate details, as, for example, the 

 markings on diatoms. With this new instrument 

 these fatiguing adjustments are avoided, and we feel 

 ■ sure that it will be cordially welcomed by the micro- 

 grapher. The construction of the Hofmann camera 

 lucida will be under- 

 stood by the sub- 

 joined diagram. It 

 will be seen that it 

 consists of c, a com- 

 bination of lenses. 

 The image is received 

 by a silvered glass, 

 a, and is reflected 

 upon the second 

 glass, b. « is a small aperture, through which not 

 only the image in the mirror can be seen, but also 

 the pencil and paper, d are two very slightly convex 

 lenses, which may be used together or separately; 

 they serve the same purpose as those on the ordi- 

 nary forms of camera lucida. The Hofmann camera 

 lucida is really a "camera lucida ocular," the in- 

 ventor intending it to replace the ordinary ocular. — 

 F. Kitton. 



Journal of the Royal Microscopical Society. 

 — Some twelve months since the Society was informed 

 by the publishers of the "Monthly Microscopical 

 Journal" that in consequence of that work not being 

 , a pecuniary success, the arrangement existing between 

 them must terminate. The Society thereupon de- 

 termined to follow the example of other societies and 

 publish their own Transactions. In accordance with 

 this resolution, the first part made its appearance in 

 March, 1878, a part being published every alternate 

 month. We have now before us the first volume and 

 part i. of the second. Volume i. contains 402 pp. 

 of letter-press, 1 7 plates and many woodcuts. The 

 names of the contributors of original papers guarantee 

 their value. 



The following gentlemen have already sent papers : 

 H. Sorby, F.R.S., &c. (Presidential Address) ; Carl 

 Zeiss, Jena; Adolph Schulze, Glasgow ; J. W. Stephen- 

 son, F.R.A.S. ; G. G. Stokes, M.A., D.C.L. Oxon., 

 LL.D. Dublin, &c. ; Professor R. Keith ; F. H. 

 Ward, M.R.C.S. ; F. H. Wenham, F.R.M.S. ; F. 



Crisp, LL.B., B.A. &c. ; Professor Owen, F.R.S- 

 &c. ; Dr. R. Pigott, M.A., F.R.S. &c. ; H. J. Slack, 

 F.G.S. ; Dr. H. D. Schmidt, New Orleans, La.; 

 M. P. Petit, Paris ; Rev. W. H. Dallinger. 



Amongst the important original articles we would 

 especially direct attention to the following, ' ' On the 

 Measurement of the Flagella of Bacterium, a Con- 

 tribution to the Question of the Ultimate Limit of 

 Vision," by the Rev. W. H. Dallinger (2 plates). It 

 has been asserted that any object whose dimensions 

 were less than a half- wave length of white light, was 

 incapable of being seen, however much our objectives 

 were improved in their revolution or definition. In 

 fact, that light was too coarse a medium for objects 

 less than m hi mcn m breadth, that being the length 

 of half a wave of white light ; supposing the blue 

 rays were used, the dimensions might be reduced to 

 about the m ' 6 Q inch without becoming invisible. 



The Rev. W. H. Dallinger, with the careful manipu- 

 lation for which he is so justly celebrated, has not only 

 been able to see the flagella on Bacterium termo, but 

 has succeeded in accurately measuring their diameters, 

 and he finds that the mean of two hundred measure- 

 ments is nearly jj-^ro inch, being much less than 

 a quarter -wave length of white light. Mr. Slack, 

 F.G.S. , the present president, communicates some 

 interesting observations " On the visibility and optical 

 aspects of Hairs viewed from a distance." He 

 finds that a hair j§^ inch in diameter when stretched 

 on a pane of plate glass and viewed against a white 

 sky, was seen by several persons at a distance of thirty- 

 four feet, and under special conditions at a much greater 

 distance. In the February number Dr. Royston 

 Pigott, M.A., F.R.S. &c, has a learned and valuable 

 paper on a similar subject, viz., " The Limits of 

 Microscopic Vision." In this paper he very much 

 increases the limits of visibility, but we must refer our 

 readers to the paper itself, our space only permitting 

 this brief notice of it. Professor Owen in his article on 

 the microscopic structure of the fossils called "grani- 

 cones" (2 plates), shows with great probability that these 

 bodies are the dermal scutes of some Lacertian reptile 

 resembling the recent Moloch horridus of Australia. 

 Associated with these remains are the bones of mar- 

 supials. The "granicones" occur in the "Feather- 

 bed " stratum, Middle Purbeck, Dorsetshire. Those 

 interested in the study of the Diatomacea; will read 

 with pleasure M. P. Petit's description of new diatoms 

 from New Zealand and Campbell Island (translated 

 by permission of the author, with notes by F. Kitton). 

 It is illustrated with two plates of figures. The notes 

 and memoranda form an important part of each number. 

 They are selected (and where necessary translated) 

 from the current literature, English and foreign ; the 

 ordinary microscopist is therefore kept "posted up" 

 in the most recent labour of foreign observers. In 

 the bibliographical division we have first a list of 

 microscopical works recently published (English and 

 foreign) ; second, an index to the contents of the various 



