59o 



NA TURE 



{Oct. 18, 1 88; 



the public, and they deserve the utmost condemnation. If 

 physiologists can make out a case for themselves, I for one am 

 prepared to give it the utmost attention, but they must not bring 

 to their aid false illustrations from a branch of science with 

 which I think I may be permitted to say I have had a large 

 experience. Lawson Tait 



Birmingham, October 6 



It seems sufficient for me to observe, in reply to the above, 

 that before writing my review of "Physiological Cruelty" I 

 took the trouble to acquaint myself thoroughly with the latest 

 edition of Mr. Tait's pamphlet. George J. Romanes 



Breeding of " Hapale jacchus " in Captivity 



Mr. Moseley's Marmosets (Nature, vol. xxviii. p. 572) are 

 by no means the first instance in Europe, or even in England. 

 Edwards, more than a hundred years ago, recorded a case in 

 Portugal ; and Frederic Cuvier had three born in Paris in 1S19 

 (vide Sir William Jardine's Natural Library — Mammalia, vol. i.). 

 A relative of mine brought a pair of this species from Pernambuco 

 in 1863, and kept them in his kitchen at Surbiton. In April, 

 1865, I was shown two living young one-; which had been born 

 a few days before. In the Proc. Zool. Soc. for 1835, births of 

 marmosets of an allied species (//. penicillatus) have been 

 chronicled as occurring in this country. W. C. Atkinson 



Streatham, S.W., October 13 



TELESCOPIC WORK FOR THE A UTUMN 



WITH Mars, Jupiter, and Saturn so favourably visible 

 in the sky during the ensuing autumn and winter 

 months, we think it may be interesting to call attention 

 to some of their more prominent features, and to ask 

 amateurs and others who devote themselves to the at- 

 tractive field of planetary observation to make a com- 

 bined effort, not only to substantiate such facts as are 

 already known with regard to the physical appearances 

 of these bodies, but to endeavour to glean something 

 new concerning them. For, notwithstanding the diligence 

 with which these planets have been scrutinised in past 

 years and the many curious facts that have been brought 

 to light, it must still be confessed that there remains 

 much to be done. Our knowledge is admitted to be ex- 

 tremely incomplete. The powerful instruments of the 

 present day do not seem capable of rendering us efficient 

 aid in this respect ; indeed we shall find by a comparison 

 of results that we owe most of our discoveries to tele- 

 scopes of moderate aperture. The real explanation 

 probably is that, with increase of aperture, definition, 

 especially of the brighter planets, becomes less perfect. 

 Faint markings are obliterated or seen unsteadily and 

 uncertainly in large instruments owing to glare, the 

 difficulty of getting a sharp, hard disk with so much 

 light, and the constant undulations of the atmosphere. 

 With moderately small instruments the conditions are in 

 many respects more favourable. The image is sharply 

 defined, and though the quantity of light may be some- 

 what deficient, there is an absence of glare and of that 

 atmospheric interference which are inseparable from 

 large apertures. Moreover, the eye is more capable of 

 prolonged observation and is enabled to glimpse the 

 faintest details on an image of moderate intensity. The 

 deficiency of light in small instruments is therefore to 

 some extent a recommendation when it is accompanied 

 with extreme sharpness of definition and when the 

 amount collected by the object-glass or speculum is 

 sufficient to allow a power to be used which displays a 

 fairly large disk without destroying the quality of the 

 definition. Indeed one great desiderative in such cases 

 is to utilise light and power in agreeable proportion, for 

 this is a very essential requirement, which is, however, 

 often neglected, and is frequently the source of disap- 

 pointing experiences. Amateurs who are careful to 

 consider these matters will be enabled, though their 

 instruments may be of comparatively small reach, to do 



much useful work in many departments of observation, 

 and particularly in that relating to planetary markings. 



With regard to Mar.-, high powers are very requisite 

 because of the small diameter of the planet. Hence a 

 fairly large aperture is necessary, for, unless the disk is 

 considerably expanded, it is impossible to trace the chief 

 features satisfactorily. In the case of Jupiter the use of 

 high magnifying powers does not apply with so much 

 force, the apparent diameter of the disk being greater. 

 But this planet is a somewhat difficult object to define 

 satisfactorily. The best telescopes will often fail to show 

 the contour of the disk with desirable sharpness. Hence 

 it is that this object with large apertures is troublesome 

 and to some extent disappointing. This is certainly the 

 case when we consider how efficiently and successfully 

 small instruments perform upon this planet, and with what 

 readiness the faintest and more minute of the details are 

 distinguished. As to Saturn, the conditions are some- 

 what different. Here there is less light and the telescopic 

 definition is better, so that large glasses possess an 

 undoubted advantage. 



The ensuing opposition of Mars is not a favourable one, 

 but many of the most interesting and now well-known 

 features of the planet may be observed in good instru- 

 ments. The curious network of " canals," as discovered 

 by Schiaparelli, and their duplication, as seen by the 

 same observer during the last opposition, in the winter 

 of 1881-82, should be looked for, as some doubts have 

 been expressed as to the reality of these phenomena. 

 The question is naturally asked, How is it that they are 

 now seen with so much distinctness again and again with 

 a refractor of only eight inches aperture, when large in- 

 struments have utterly failed to reveal them ? Schia- 

 parelli, it is true, works in a climate highly favourable to 

 such delicate work, and his telescope, though compara- 

 tively small, is yet of the finest possible quality. But 

 even with the prevailing conditions so eminentlyconducive 

 to the attainment of such important results, it must still 

 remain matter for surprise that, as the celebrated Italian 

 astronomer himself put it, " the greater number of canals 

 and of their pairs were observed with comparative ease 

 whenever the air was still, and only a few cases required 

 a special effort on the part of the observer." 



These so-called canals appear from Schiaparelli's charts 

 to be very narrow dark markings, running generally in 

 straight lines, and often intersecting each other so as to 

 constitute a perfect network about the equator and in the 

 region south of it. Many of these lines were seen to be 

 double in January and February, 1882, and the inference 

 is that, as these duplications had escaped observation 

 during the more favourable opposition of 1879, they 

 are subject to periodical variations, or in any case 

 represent phenomena of temporary character. They 

 undoubtedly exhibit a most extraordinary arrangement, 

 and such as naturally to call forth some amount of 

 objectional comment from those who, though familiar 

 with the telescopic aspect of the planet, have never seen 

 it as Schiaparelli depicts it. In fact his delineations give 

 a boldness and definiteness of outline in the smallest 

 details which no other observer is able to corroborate. 

 The extreme delicacy of shading and softness of outline 

 so characteristic of many of the features of this planet 

 as displayed in our best telescopes seem wholly wanting, 

 and we have presented to us an elaborate complication of 

 hard, dark lines which bear little analogy to our own 

 impressions. 



It has been suggested that many of these so-called 

 " canals " are the edges of half-tone districts on the planet, 

 and possibly this may be so in certain cases. But we 

 must not forget that the eminent author of these impor- 

 tant discoveries expresses himself very confidently as to 

 their existence, for he has seen them repeatedly, and at 

 times when the conditions were not favourable to the 

 detection of such difficult markings. Probably something 



