March i, 1900J 



NATURE 



4'7 



over, instead of removing a larger proportion of the 

 thinner parts of the image, which, of course, lie near the 

 surface of the film. This is an exceedingly useful effect ; 

 but here again the chemical changes have not been in- 

 vestigated, and the theories that have been suggested to 

 account for the exceptional effect are far from satisfactory. 

 It is not certain, indeed, that the remaining image is of 

 pure silver. 



The makers of apparatus are always seeking to im- 

 prove their goods, and they are, as a rule, so successful 

 that it is impossible to refer here to other than the most 

 important advances. Photographers used to be satisfied 

 with lenses that either covered a large field in propor- 

 tion to their focal length, or that had a large aperture ; 

 but these properties that used to be considered incom- 

 patible now have to be combined ; a large angle of view 

 is maintained while the aperture is increased. Instead 

 of /8, which used to be regarded as the maximum aper- 

 ture for outdoor work, we now have / 6, and even larger 

 apertures, without the introduction of the peculiar faults 

 usually associated with portrait lenses. The firm of 

 Goerz, of Berlin, has quite lately put upon the market 

 a doublet, each combination of which consists of five 

 elements, the complete objective having an aperture 

 of /5'5- These — the stigmatics of Dallmeyer at fl\ 

 and /6, the planars of Zeiss with apertures of about 

 /;4, and other lenses of similar properties — are instru- 

 ments of precision for giving an image over an extended 

 field, as telescope objectives are instruments of pre- 

 cision for giving definition over a very small field. In 

 conjunction with the rapid gelatine plates of to-day, they 

 place a power in the hands of scientific workers that 

 was not conceived possible a few years ago. 



The firm of Dallmeyer have recently improved their 

 stigmatics, series /6, by putting the combination of 

 greater focal length in the front instead of behind. To 

 use either combination alone, it is now only necessary to 

 remove the other, and the extension of camera necessary 

 is nearly the same for both the combinations, although 

 their equivalent focal lengths are approximately as 15 

 to 2, taking the focal length of the whole combination 

 as the unit. Dr. Rudolph, of Zeiss', has investigated the 

 question of the use of cylindrical surfaces in objectives 

 for the purpose of getting a different ratio of enlarge- 

 ment (or reduction) in two directions at right angles to 

 each other. One result of this work is the "anamor- 

 phot" issued by Messrs. Zeiss, and its use is chiefly, if 

 not exclusively, in the readjustment of the proportion of 

 length to breadth of designs for their application in the 

 decorative arts. 



There does not appear to have been any radical im- 

 provement in cameras of late ; but the system of cine- 

 matography, made possible by the perfection to which 

 film-supported sensitive surfaces have been brought, con- 

 tinues to engage the attention of a large number of in- 

 ventors. The most recent, and doubtless most interest- 

 ing, application of this principle is in an apparatus that 

 the Kodak Company are making for Sir Norman Lockyer, 

 for use during eclipses of the sun. The apparatus will 

 accommodate a film five inches wide and of length suit- 

 able for the required series of exposures. The opening 

 behind which the film is exposed is twelve inches long and 

 three inches wide. The apparatus is designed to photo- 

 graph a series of spectra, as of the chromosphere, so that 

 the exposures may follow each other with greater rapidity 

 and certainty than is possible when plate-changing has 

 to be done by hand. The operator has only to turn a 

 handle continuously, and at each complete revolution an 

 exposure is made, the exposed film is wound up, and a 

 new portion brought into position. Three-quarters of 

 the revolution effects the change of film ; at the begin- 

 ning of the remaining fourth the shutter is opened ; it 

 continues open until the revolution is completed, or 

 nearly completed, when it is closed ; then the film- 



NO. 1583. VOL. 61] 



changing takes place again, ancl so on. By stopping the 

 crank during the last quarter of the revolution, a time- 

 exposure of any duration may be given. It is expected 

 that the apparatus will be used in conjunction with a 

 twenty-foot objective of six inches aperture with a prism 

 in front of the objective ; and as this lens gives practically 

 no curvature on a field twelve inches in length, the film 

 will be used flat. 



Scientific photographers on the Continent have lately 

 been paying more attention to the measurement of the 

 opacities of photographic plates. Dr. J. Hartmann, of 

 Potsdam, has recently described an apparatus constructed 

 for him for comparing opacities. It consists of a hori- 

 zontal microscope with its ocular and objective, with a 

 tube branching from it at right angles, downwards, that 

 carries a second objective. At the junction of the two 

 tubes is the well-known arrangement of two right-angled 

 prisms, with their hypothenuse surfaces cemented to- 

 gether except at a -small disc in the centre of the ad- 

 jacent sides ; so that one sees a small portion of the 

 plate being tested surrounded by the comparison tint. 

 The apparatus appears to be unnecessarily costly and 

 complicated when compared with apparatuses that have 

 been used in this country for a similar purpose. 



There are many other matters that would claim atten- 

 tion in a complete rcsumd of recent progress in photo- 

 graphy, some of which have already been referred to 

 in these columns. C. J. 



THE POSITION THAT UNIVERSITIES 



SHOULD TAKE IN REGARD TO 



INVESTIGA TION. 



'X'HE American Society of Naturalists arranged for a 

 ^ discussion on the duties of universities with regard to 

 investigation, and the American journal, Science^ has 

 recently published the contributions to the discussion 

 made in the end of last year at the New Haven meeting. 

 Profs. Dwight of Harvard, Chittenden of Yale, Jastrowof 

 Wisconsin, Patten of Dartmouth, and Dr. Macdougal of 

 the New York Botanic Gardens — five distinguished repre- 

 sentatives of the natural sciences in America — made a 

 formal and deliberate expression of their opinions, and 

 an examination of these convictions cannot fail to be 

 valuable to English readers. On all salient points these 

 experts are in complete agreement. They have no doubt 

 that the connection between universities and research is 

 fundamental. Dr. Macdougal dismisses it as " axiomatic." 

 Prof. Jastrow declares that a university should be the 

 " natural habitat " of investigation. Prof Dwight is " sure 

 of a sympathetic hearing from public and universities for 

 discussion of the modes and conditions of university re- 

 search." The others differ only in the precise phraseology 

 they employ. Nor is there any doubt but that university 

 teachers should be investigators by temperament and 

 habit. As Prof Chittenden insists, the primary function 

 of a university is a diffusion of the knowledge already 

 gained, rather than the provision of new knowledge ; but, 

 although teachers who were not investigators have existed, 

 the ideal teacher must be more than a diffuser. All uni- 

 versities of standing make success in investigation a 

 necessary qualification for their teachers, and, in effect, 

 our witnesses all agree that, having chosen rightly such 

 men, it is the duty of the universities to see that time 

 and opportunity for investigation should be found for 

 them during their tenure of office. 



There is a certain divergence of opinion as to the ex- 

 tent to which original investigation should be made an 

 actual part of the training of students. Prof Dwight and 

 Prof Patten are not inclined to encourage it, the former 

 thinking chiefly of medical students and agreeing with 

 Huxley, that whoever adds one tittle of what is un- 

 necessary to medical education is guilty of a very grave 



