JlTNK, 1901.] 



KNOWLEDGE. 



141 



Conducted by >r. I Cross 



Fine Ap.iustmknts — In the details of th>^ construction of 

 microscopes, as in fact in every other instrument or machine, 

 there is no re-al finality, and each year sees the introduction of 

 some slight improvement which may tend to make work easier 

 and more accurate. A study of the catalogues of the various 

 microscope manufacturers of a year or two ago wiil afford food 

 for reflection, for nearly every noted maker then expressed hi.s 

 unbounded confidence in his particular form of fine adjustment. 

 One states that his " must be considei-ed to be a triumph of 

 mechanic;!! skill," another " has proved absolutely satisfactory," 

 and a third " its reliability is unsurpassed." Yet within the 

 space of a few months nearlj- all the leading makers found it 

 ilesirable to introduce new devices for fine adjustments. All of 

 them have distinctive features, indicating that care and con- 

 sideration have been given to their design, and it will probably 

 prove of interest to readers to be made acqu.ainted with such 

 particulars as I have been able to collect from the various 

 makers, for every new idea which enables the worker to manipu- 

 late more preciselj" than available means have permitted him 

 formerly to do, should receive both consideration and recom- 

 mendation. 



A perusal of the paper read before the Royal Microscopical 

 .Society, by Mr. E. M. Iselson, and reported in the Society's 

 Journal for August, 1899, on the "Evolution of the Fine 

 Adjustment," conveys some idea of the gradual improvement 

 that has taken place in tliat movement. 



Those who use a substage condenser giving a small aplanatic 

 cone will probably not feel the necessity of a better fine adjust- 

 ment than that which is usually fitted to student's stands havin" 

 the direct pillar action. 



Directly an illuminating cone bearing a fair proportion to the 

 nnmericiil aperture of the objective is used, the necessity for a 

 slow and precise movement by fine adjustment becomes over- 

 whelmingly apparent. 



In a previous article T referred to the fact that many new 

 substage condensers yielding large cones of illumination had 

 been recently introduced, and as the supply of such articles 

 must indicate a demand, it necessarily follows that people who 

 have used them have discovered the weakness in the fine adjust- 

 ments of their instruments, have called for something better, 

 and response is being made by manufacturers to meet this fresh 

 demand. 



There are four new fine adjustments which I propose to 

 review, as follows : — The Continental pillar fine adjustment 

 with levers, designed by Reichert, of Vienna ; the new fine 

 adjustment fitted to their photo-micrographic stand, by Zeiss ; 

 the " Ariston," by Swift and Sons ; and Stringer's fine adjust- 

 ment, by W. "Watson and Sons. 



Reichert's Fine AiucsTMENT.— The great weakness of the 

 Continental pillar form of fine adjustment ha'' been consequent 

 principally on the difficulty of producing a sufficiently slow rate 

 of movement with a direct-acting screw that would stand wear 

 and tear. The problem has been met by Reicliert's device, 

 which consists of a screw, having a point which engages two 

 lever arms, the upper pressing upon the lower, and being 

 mounted from the outer .sides of the pillar. To the under sides 

 of these levers is attached a piece of hemispherical shajied 

 meta:, which has on its curved side a point which communicates 

 the motion. 



A reference to the illustration in our next number will make 

 this otherwise obscure description quite clear, and it will be 



further seen that the rate of movement is dimini.sbed by the 

 proportions of the lever arms, which are .about i\ : 1. This 

 would mean that if a screw of the ordinary kind were used, the 

 rate would be reduced to ^J,^ in. for each revolution instead of 

 .jJj^j in. as in the old pattern. 



(The illustmiiou referred to in the alcove note will appear iu the July 

 number of Knowledqk.J 



The Mrcnoscoi'F, ..\nt) the Phaumaceutical Che mist, — To 

 the bus}' medical practitioner, reference to the microscope for 

 diagnostic purposes is a matter of every-daj' occurrence. Those 

 who have not the time or disposition to do the work them- 

 selves, have at their disposal associations and laboratories which 

 cater for their special needs. In addition to these facilities, it 

 is becoming usual for pharmaceutical chemists to make them- 

 selves acquainted with the wants of medical men in these respects, 

 and to be prepared to make the examinations, and to provide 

 themselves with the necessary modern apparatus for so doing. 



The microscope; is becoming increasingly important in the 

 curriculum of the pharmaceutical student, and it is in no small 

 degree due to this profession that so much of our food and 

 drugs that once were adulterated, arc now purer and of better 

 quality. Powdered drugs and spices were frequently mi.Ked 

 with starches, flour, etc., but the microscope ((uickly discloses 

 such foreign materials. The knowledge of active constituents 

 and other cell contents of medicinal plants, and their distribution 

 in different tissues and organs is becoming increasingly com- 

 prehensive and accurate, and experiments aided by the use of 

 special micro-chemical reagents are in progress to identify the 

 vegetable alkaloids and related substances raicroscopicilly. 



It is a satisfaction to know that work of so thorough a nature 

 is in progress, and it is a guarantee that with increased and 

 more general expert knowledge, our food, drugs, and other 

 commodities will be purer and finer than they have been. 



The WiiKKSHoi's of E. Leitz, Wetzlar. — A correspondent 

 sends a description of his visit to the microscope factory of this 

 noted optician. The following is a short ivsumi; : — 



50UI) microscopes per annum is the output of this house, 

 leading one almost breathlessly to ask " "What becomes of them 

 all '? " Leitz's gre.at feature is that he confines himself entirely 

 to microscopes and their accessories, instead of producing 

 scientific instruments of every description as English opticians 

 generally do. Herein lies the secret of his success. 



With a large and regular demand for certain fixed models, a 

 system of production in which machinery plays an important 

 part is possible, and ensures sound construction with a minimum 

 of cost. The supervising and testing departments are of the 

 most thorough description, and when the care that is taken is 

 known, it is not to be wondered at that the Leitz objectives are 

 credited with being more uniform in quality than any others. 



It has many times been stated that the reason why Con- 

 tinental houses produce cheaply is because they employ women 

 workers. Leitz has no female labour at all ; all his men are 

 skilled mechanics, the majority of whom have been trained in 

 the works. 



It is quite possible for English houses to compete successfully 

 with foreign competitors if they do but adopt their methods, 

 which may be summarised in a few words. Have the works in 

 a country town where rents are low, and the cost of living less 

 than in London. Have suitable buildings for workshops, and 

 the rest is a matter of system and machinery. 



NOTES AND QUERIES. 



//. Deo-ey. — The two books that are likely to give you the 

 information you require are "A Populir Hand-book to the 

 Microscope," by Lewis Wright, price 'Js. 6d., and " Modern 

 Microscopy," by Cross and Cole, price 3s. 6d. More costly 

 works are "The Microscope," by Hogg, new- edition, price 

 10s. 6d., and '" The Microscope and its revelations," by 

 Carpenter, edited by Dr. D.illinger, a now edition of which is 

 promised for next July. 



Chalk wit»Siii;lls. — In a previous nutnber I ofE.>red to 

 send a correspondent a supply of Foramintferous Limestone. 

 Several readers have asked that I would also give them some. 

 I shall have much pleasure in complying with their requests if 



