112 



KNOWI.I Ix'.l 



MaK(II. 1912. 



Ireland. S. In the other districts it was generally in excess, 

 thiiMKli the departmis from the tnean were inconsiderable. 



Sunshine «as sli(;htly in excess in Scotland. N., and in 

 England, N.W., but was in defect elsewhere. In Scotland, 

 W., the daily mean was only ()-6 hour (7%). The sinmicst 

 station was dreat Yarmouth, where the daily mean was 3-0 

 hours (40 %l. .At Westminster the duration averaged 0-9 hours 

 (10 ",.•; at Hampstead in contrast with the previous week the 

 aver.ige was less, 0-fi hours(7 ",. ). The mean temperature of 

 the sea water ranged from 36° -2 .it Croinarty to 45' -8 at 

 Salcombe. 



MICROSCOPY, 



conducted with the assistance of the following 

 iiiicroscopisls : — 

 AuTHiR C. Hankibi.I). Arthur Eari.anii, K.K.M.S. 



Richard T. Lewis, F.R.M.S. 

 Chas F. Rousselbt, K.R.M.S. 

 D. J. ScoiRHELD, F.R.iM.S. 

 C. D. Soar. F.I..S.. K.K.M.S. 



The Rkv. K. \V. B(im 

 James I',i;rton. 

 Charles H. Caffvn 



j# 





£ 



X) 



LOWPOWKK PHOTO- 

 MKKCU.K.VPHV WTIH- 

 OL'T A MlCKOSCOl'i:.— 

 This note is chiefly con- 

 cerned with home - made 

 contrivances of a very 

 simple character, designed 

 to be of service in simple 

 low power photomicro- 

 graphy. By this latter term 

 is meant that region of 

 work between the ordinary 



copying " of everyday 

 photography, and the more 

 .1 m 1) i t i o 11 s angiiioiitatioiis 

 which necessitate the use of 

 a microscope as well 

 as a camera. In this 

 chapter a microscopt 

 is not used, but con 

 trivances are shown 

 which enable us to \isc 

 ordin.iry micro-objec- 

 tives of low power, 

 i.e., an inch or so. 

 When lenses of foc.il 

 length not less than 

 two inches (say tw^ • 

 to four inches range 

 are to be employed 

 with any ordinarx 

 quarter -plate camera 

 of, say. twelve inch bellows Icngtii. it is clear that we 

 cannot get any very great magnification or ratio of image 

 to object, li "ill. Ilicrcforf. be desinililc to .nis^ment tlie 



Figure 109. 



camera length in some way. One convenient plan is by 

 the use of a mi^tal tube, one end of which screws into the 

 ordinary camera-lens flange, the other end cut with a similar 

 thread to take the lens to be employed. It is a further 

 convenience to have this tube in two pieces AB and CD. as 

 shown in Figure 109, so that we may use one or both pieces 

 according to our desired degree of magnification. 



The end A screws into the flange on the camera front, 

 B and C join up together. D is here closed by an " adapter " 

 to take any ordinary micro-objective. E is a two-inch Zeiss 

 protar with lens cap F. The size of this particular tube is 

 large enough to take a Wray four-inch U.K. or \V ray three-inch 

 platystigmat, both exceedingly useful tools for natural history 

 work, e.g., insects, fossils, shells, parts of plants, and so on. 

 Lenses of these kinds are already provided with stops or 

 diaphragms, but when the worker is using ordinary long focus 

 te.g., two-inch) micro-objectives, it is often of very great service 

 to use also a contrivance known as a Davis shutter. This is 

 shown in Figures 1 10 and 111. where we see the two sides of the 

 micro-objective adapter that 

 was similarly lettered in Fig- 

 ure 109, and also two views 

 of the "Davis "which is really 

 a separable iris diaphragm 

 contrivance. As this cannot 

 be put inside the lens it is 

 screwed in to the adapter, 1. 1'., 

 between D and the objective 

 in use. The worker will find 

 it very convenient to cut a 

 card wedge showing points 

 of width one-, two-, three-, 

 and so on, tenths of an inch. 

 This wedge is inserted into 

 the iris which is then closed 

 just to grip it and the 

 pointer outside cor- 

 respondingly marked 

 one-, two-, three-, and 

 so on. We can thus at 

 any time close down 

 the "pupil" to any re- 

 quired size by means 

 ofthepointerand scale. 

 It should be remem- 

 bered that the expos- 

 ure normally will vary 

 as the squai'esof these 

 numbers. Thus, two- 

 tenths diameter passes 

 four times, and three- 

 tent lis nine timcs.a.s much light as the one-tenth diameter opening. 

 .V glance at the table will make matters clear in a moment. 

 Sii])posi< the lart;cst ,iprrt:ir<' is half ,iii inch. ;.('.. five-tciitlis. 



R> 



^ 



iM'.iKi: II. 



