350 



KNOWLEDGE. 



September, 1913. 



shoe, B, while the camera end rests on a two-legged shoe, C. 

 All three of these legs are adjustable by means of screws, so 

 that the apparatus can be levelled on a non-level table. [This 

 special table is not an essential part of the outfit. A friend 

 has a similar piece of apparatus which is supported on a shelf 

 firmly bracketed to the wall, and finds this entirely satisfactory.] 



Now briefly to enumerate the parts. AA, the square base 

 bar, arranged with its diagonals vertical and horizontal ; B, 

 the one-legged support, here shown resting on a thick pad of 

 pieces of cloth (the best absorber of vibrations that I know 

 of) ; D, the first sliding shoe, into which screws a round 

 vertical metal rod or lamp support ; E, the gas tap for 

 light, which by a screw can be fixed at any desired height ; 

 E is connected to the gas supply by a piece of rubber tubing ; 

 F is the holder of an inverted gas mantle. I find the " Howelite " 

 excellent, the light is intensely brilliant and steady, and the 

 mantles stand a surprising lot of rough usage. When not in 

 use I lift off the part F carrying the mantle and slip it on to a 

 piece of round wooden rod fixed into a loose triangular foot, 

 and keep it in one of the drawers. The next four sliding shoes 

 have vertical brass cylindrical pillars screwed into them. Inside 

 each pillar another tube slides. This latter can be fixed at any 

 height by a clutch screw collar, the upper part of the outer 

 tube being cut in two places so as to permit of the taper 

 thread forming a throttle grip. The first of these pillars G, 

 i.e., the one next the lamp, carries a " paralleliser " or 

 condensing lens of the crossed lens type which can be centred 

 by three screws and springs. H, the next pillar now un- 

 occupied, can hold a water tank if required. The one, J, here 

 carries a contrivance for holding a two-inch square colour 

 screen in three sides of a square rebate or groove. On the 

 other side of the circular head are two spring clips like those 

 on the stage of a microscope. These we may use for other 

 colour screens, and so on. J can also be used as a stage 

 object holder for such things as shells, fossils, suitably 

 mounted, and so on, when photographing with a short focus 

 objective without the microscope. K, is another shoe and 

 pillar not occupied at the moment. L, the microscope with 

 M, a sliding baffle tube embracing (without touching) a 

 projecting short tube in front of the camera, thus providing a 

 light-tight joint between microscope and camera, but without 

 contact between these two pieces. P, the bellows of the 

 camera, is prevented from sagging by a shoe and sliding pillar 

 arrangement Q. At C, we have the two-footed support (cloth 

 has been removed to show details). R, is a reflector or mirror 

 on a separate tripod foot and sliding pillar with knuckle joint 

 at the back, fixed at any angle at will by a screw. Thus one 

 can stand at any place along the table edge and yet see the 

 reflected image of the focusing screen in this reflector R. On 

 the further side of the base bar is a long steel rod. At one 

 end is S, a large milled head used for working the fine adjust- 

 ment of the microscope. At the other end, here out of sight, 

 but shown in Figure 383, is a grooved circular disc U. This 

 carries a silk cord which passes round the head, T, of the fine 

 adjustment. Details shewn in Figures 378-382 — V, is a pulley- 

 weight which keeps the silk cord taut and of even tension. 

 Going round the camera end of the table we get the view 

 shown in Figure 383, where S is the head of the fine adjust- 

 ment focusing rod. C is the two-legged support here shown 

 resting on pads of cloth. At R we see the back of the mirror 

 holder with screw knuckle joint, sliding pillar, and tripod foot. 

 At U is placed a pointed bit of white card to indicate the 

 grooved disc on the focusing rod which carries the silk cord 

 focusing tackle. In this view we see how the camera is 

 supported on two U-shaped or forked uprights (detachable), 

 so that the camera can be adjusted at any height by the 

 screws, b, b. By removing the butterfly screws, a, a, the two 

 supporting forks lift off their respective sliding shoes. The 

 sagging of the bellows results from removing the supporting 

 pillar, Q, seen in the first view. 



Figure 380 shows us a little more detail as to how the 

 microscope is supported on the metal table, d, d, which is 

 fixed to its own pair of sliding shoes by the butterfly nuts, 

 d, d. The three feet of the microscope fit into three ring 



collars, e, e, e, on the base plate. At / is shown a contrivance 

 like a shallow pill box lid of white card. This fits the distal 

 end of the sub-stage condenser at g. On this are drawn two 

 or three concentric circles in black lines by compasses. When 

 this light-adjusting cap is in situ at g it greatly helps in 

 adjusting the positions of the lamp, E, F, and lens, G, so as 

 to get an even image of the mantle mesh truly centred. If 

 now we open the camera back and look through the 

 microscope tube we can see at a glance (/ being removed, of 

 course), if our light, F, and lens, G, are on the axis of the 

 tube. At h we see a new form of speculum condenser con- 

 sisting of a stout clear glass rod polished at one end 

 and ground at the other end. Before leaving this figure 

 we may glance at the silk cord and then see 

 it in detail in Figures 378 and 382 ; this being, so far as I 

 know, an entirely new design. The letters T, U and V as 

 before refer to the milled head of the fine adjustment screw, 

 the grooved wheel on the focusing rod, and the weight with 

 pulley head. The pulley head is notched, so that it can be 

 easily detached. The cord is also easily lifted off T and U, 

 so that it remains only attached to the table d, d. It may be 

 noted that the edge of the table under the pulley wheels of the 

 table is cut away on both sides to facilitate the unshipping of 

 the focusing tackle. The silk cord is so arranged that at no 

 part of its course does the cord rub against itself, and there 

 is quite even tension at T. i.e., no side-pull at all. 



Figures 379 and 381, show us the arrangement for the light- 

 tight connection between the microscope and camera. At 

 M we have a double tube, which, by means of a collar, 

 slides freely on the inner draw tube K which may or may not 

 carry an eye-piece as we may desire. Between these (inner 

 and outer) tubes goes a similar flange-mounted tube, N, on 

 the front of the camera as shown in Figure 381. The camera 

 has a loose panel front fixed by four turn buttons, so that 

 short-focus photographic objectives may be used without the 

 microscope in conjunction with certain other contrivances 

 which may be held over for a further note. 



This apparatus has been especially made for me under the 

 supervision of Mr. W. R. Biss (106, Elmore Street, 

 Canonbury, London N.,) who is an enthusiastic amateur in 

 microscope and camera matters, and to whom is due the 

 credit of designing many of the contrivances above mentioned. 



F. C. Lambert, M.A., F.R.P.S. 



CORRECTION. — By an accident the blocks of two figures 

 on page 272 [Volume XXXVI (1913)] have been inter- 

 changed. The description of Figure 285 should, therefore, 

 read " Pisidium obtusale " which is the most globular 

 species, and Figure 293 should be P. millium, the squarest. 



PHOTOGRAPHY. 



By Edgar Senior. 



PLATINUM TONING.— Although the toning of silver 

 prints by means of a salt of platinum has not been practised 

 to anything like the extent that gold toning has, the method is 

 nevertheless a useful one, and at the same time capable of 

 giving excellent results either when used alone or following 

 after a preliminary toning with gold. The use of platinum 

 salts in toning certainly dates back at least forty years, but it 

 cannot be considered as having been successful until the 

 introduction of the chloroplatinite of potassium by Mr. Willis 

 for platinotype printing, as attempts to use the ordinary 

 tetrachloride of platinum more often than not resulted in 

 failure. One of the earliest, perhaps, to devise a really 

 simple and satisfactory process of platinum toning was the 

 late Mr. Valentine Blanchard, who supplied a matt surface 

 printing paper together with the toning solutions for the prints 

 made upon it. Since then, however, numerous formulae 

 have from time to time been published for the toning of silver 

 prints with platinum that leave little to be desired. Collodio- 

 chloride papers especially give good results when toned in this 

 way. When the treatment with the platinum solution follows 

 toning with gold the following method may be recommended : — 



