48o 



NATURE 



[February 8» 19 12 



Temxyaon and his Friends. Edited bv Hallam Lord I 



Tennyson. Pp. xiii + soj. (London : .Mucmillan 



and Co., Ltd., 1911.) Price los. net. 



This interesting collection of .articles and remini- 

 scences, nearly all by the personal friends of the late 

 Lord Tennyson, and brought together by his son, will 

 be a valuabli' addition to the Tennyson literature. 



The book may be looked upon as a supplementary 

 volume to the Memoirs, which appeared about four 

 years after his death, for it gives a still further 

 insight into the life, friendships, and opinions of the 

 great poet. 



A description is given of the early days in Lin- 

 colnshire and of the Somersby friends; also of his 

 two brothers, Frederick and Charles, who were 

 nearest him in age, and w-ith whom he was most 

 closely associated in school and college days. 



Other articles give his intercourse with Lushington, 

 Fitzgerald-, Carlyle, Thackeray, Clough, and many 

 others. 



Tennyson's attitude towards science is shown in 

 articles'by Sir Norman Lockyer and Sir Oliver Lodge. 

 The fornier points out "his unceasing interest in the 

 causes of things, and in the working out of nature's 

 laws," and compares him with Dante in this respect, 

 more especially in the way he kept abreast of his 

 time. 



To the articles, some of which are reprints, are 

 added several of the poems written by Tennyson to 

 his Cambridge friends and to those of later years. 

 The collecting into one volume of these many writ- 

 ings of interest cannot fail to give pleasure to all his 

 admirers. 



LETTERS TO THE EDITOR. 



[The Editor docs not hold' himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of. rejected 

 manuscripts intended for tiiis or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Microscope Stands. 



The discussion on microscope stands will do little good 

 if it is directed towards the production of a universal type 

 of instrument. .As a maker of microscopes, I come into 

 close contact with many branches of work the requirements 

 of which are totally different. To make but one form 

 would be a fatal mistake. The metallurgist cannot use the 

 instrument which is best suited for the bacteriologist, 

 neither will the Rosenhain metallurgical microscope suit 

 the biologist. The Dick petrological microscope is quite 

 unsuitable for the entomologist, and the binocular instru- 

 ment, which demands long tubes and a great range of 

 focus for the use of the lowest powers, will not satisfy 

 the chemist. For the use of botanists, zoologists, and 

 bacteriologists there is a certain similarity of requirements, 

 but even here it would be unwise to endeavour to make all 

 microscopes on one model. The work of the student in 

 the botanical laboratory is totally different from that of 

 the research worker who is making photomicrographs with 

 the highest power immersion lenses. 



The development of the microscope in the future will 

 probably be in the direction of producing specialised types 

 for specific work. Thus discussion on microscopes in 

 general rather than of definite types is difficult, and is 

 liable to become discursive. It can also only be mislead- 

 ing to Set up a false comparison between English and Con- 

 tinental types. No such types exist at the present time. 



English microscopes are made which are almost fac- 

 similes of instruments of Continental manufacture, and 

 although Continental makers were slow to realise the 

 advantages of the more perfect adjustments provided from 

 the earliest days in English microscopes, they have com- 

 menced to do so. The so-called Continental mechanical 

 stage was invented by John Mayall, and placed on the 

 market by at; least three British firms before it was applied 

 to foreign microscopes, and therefore the terms English 

 NO. 2206, VOL. 88] 



;,,.,( (°'>'<'inental have no meaning as dewrrihlnf ivn.. 

 !-.. A few queiitiuns which apply 

 iv be discussed gj^nerally, but the : 

 puiiitu tiiust b<! considered in connection with ih- 

 of work for which the instrument is required. 

 The; comparison of rigid as again<>t sprim 

 the adjustments applies to all classes of tl. 

 and a full discussion of this point can, in my ",'.' 

 lead to one conclusion. The microscope must, 

 things, have adjustments which arc rigid and it- 

 spring or tremor. They must be absolutely firm, and 

 must respond to the slightest movement without *-i 

 backleash or sag. The adjustments consist of m'-' 

 worked by a screw, either direct or by means of .1 

 cam, or by a rack and pinion. For the fine aii 

 the sliding portion must be kept up to its work by 

 to prevent backleash. The slides or fittings of 

 scope must be the very finest that skill can create, 

 to s»?cure this they must fit throughout their entire l< 

 or the greater portion, and not at a few small po 

 being scraped or ground, so that the whole of the surl 

 bed together ; thus only can a perfectly rigid slide 

 from swerve, backleash, and tremor be obtained. If 

 is done, the wear that takes place during many V' 

 constant use will be quite inappreciable, as there is no 

 on such fittings. The provision of spring pieces to tak 

 wear is not only unnecessary, but injurious, because 

 such spring pieces come into play, the fittings will h- 

 forth depend on the friction at a few points Instead 

 largo surface. 



Such fittings are not stiff, and become loose be* 

 they bear at a few points only, and are held up by sr 

 which are liable to shake loose. It may be argued 

 if the slides were fitted accurately and the spring [> 

 were inoperative, only being there for use in case of v 

 an advantage would be gained. That is not don 

 practice, for if the screws holding the spring pieces 

 slide so made are released, it will be found to be . 

 loose. Moreover, it requires a skilled workman to s> 

 the slide of a slow motion fitted with such spring i> 

 to obtain a perfect motion free from backleash or 

 and it is much better that he should refit the original 

 fitted slides. Spring fittings are mechanically w : 

 this purpose. Who would think of having an 

 spring fitting for a theodolite centre? The qualii> > 

 adjustments, more especially the fine adjustment, 

 scarcely been alluded to, but this is the most impo 

 adjustment of the instrument. I am of opinion that 

 original form of a micrometer screw and a lever has ; 

 been equalled by the more elalwrate cams recently i 

 duced. The smaller the number of parts that go to r 

 the mechanism, the fewer the points of contact or ' 

 ings to give that slight sag at the reversal of the ni 

 which makes it so difficult to obtain the best focus 

 high powers. 



As to the form of a microscope, its stability doe- 

 depend upon whether the base is of the tripod or so-i 

 horseshoe pattern. It is universally admitted that it s! 

 stand on three points, and the test of stability that si 

 be applied is. at what angle will it upset, and what ; 

 is required to make it do so. 



Some tripods are more unsteady than some of the b 

 shoe-pattern stands, and vice versA. It is merely a l 

 tion of the position of the three points on which the ir 

 ment stands compared with its centre of gravity 

 weight. As probably nine-tenths of the small con 

 microscopes sold are of horseshoe and pillar patter 

 may be concluded that an overwhelming opinion exi> 

 favour of this type for ordinary botanical and m^ 

 work. This is probably because the substage is ren 

 more accessible, and the stability produced by a 1 

 base is preferred in a compact instrument to that obt 

 by a lighter stand with a greater spread to the feet, v 

 also occupies a larger space. The large tripod ba- 

 supplied on some of the best research microscopes is • 

 .ibly the most perfect stand for stability, but the la 

 legs are more or less in the way of the manipulati. 

 substage apparatus. The design of the mechanical - 

 is an illustration of the necessity of specialised stand - 

 different classes of work. If the mechanical stage i-^ i"' 

 corporated in the instrument its travel is greatly limite^ 

 , as it fouls the condenser or the large ilhimir..itinj 



