HARDWICKE'S SCIENCE-GOSSIP. 



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as previously recommended, the image thrown on the 

 tracing-paper at about 20 inches distance from the 

 object will not be as highly magnified as if seen with 

 the eye-piece down the microscope tube. A i-in. 

 objective will magnify about 30 diameters instead of 

 50 diameters. 



Among the advantages of this camera apparatus is 

 that of enabling one to obtain intermediate magni- 

 fying powers, in fact it is in itself a microscope stand. 

 By using only the objective of the microscope fitted 

 on to the end of the conical tin tube by means of the 

 india-rubber cone, a magnified image of any object 

 may be cast upon the tracing-paper. With the i-in. 

 objective used in this way the magnifying power will 

 be about 15 diameters. If the box were made so 

 that the distance of the paper could be varied, any 

 amplification might be obtained although with loss of 

 light and definition at long distances. If such a 

 camera were desired it would no doubt be better to 

 buy a photographer's bellows-camera, which could be 

 used for drawing objects by substituting a sheet of 

 plate-glass and one of tracing-paper, for the ground- 

 glass used for focussing on. A photographer's tripod 

 stand would also be convenient for inclining the 

 camera at any angle. 



In order to support slides in front of the camera, 

 when the microscope stand is not used, I have made 

 a simple holder as follows : — 



Two slips of wood, about 4 in. high, have a slit 2 in, 

 long, and broad enough to admit the slide edgewise, 

 cut in them with a fret saw. These uprights are joined 

 by a cross piece at the bottom, and stand 2 in. apart. 

 The cross piece is fastened by a hinge in the middle 

 to a flat oblong board 6| X 3 in. so that the uprights 

 stand equidistant from each end, and can be inclined 

 at any angle. Near the end of the board, behind the 

 uprights, two small oblong holes are made, into which 

 two small pieces of wood are fastened by pins driven 

 from the edge of the board. These "struts" serve 

 to support the uprights as they turn on the pins, and 

 their upper ends are cut off at angle of about 45 

 degrees, so as to make them fit into notches in the 

 back of the uprights. This holder might be placed 

 on a book, but if four brass shutter-screws turning in 

 brass pieces let into the board were added, it could 

 be raised or lowered as desired. By using two 

 boards, the upper sliding on the lower, and a shutter- 

 screw or rack and pinion in a horizontal position, 

 probably it would be easier to focus. 



Another plan of holding an object which* I find to 

 answer beautifully, is to use the microscope stand as 

 a holder merely. If the limb be placed in a hori- 

 zontal position, the body racked back out of the way, 

 the mirror, and, if possible, the pivoted limb holding 

 it turned aside, the slide may be held in the ordinary 

 clip. The upper side of the slide should be turned 

 downwards, and the tube of the camera brought to 

 coincide with the centre hole of the stage. By 

 bringing the electric or any other available light 



between the body and the stage or "above the 

 stage," the magnified image will be thrown on the 

 paper-screen of the camera. A diagram of this ar- 

 rangement is given in my article last month, page 172. 



The ease with which the magnifying power can 

 be ascertained by the actual measurement by this 

 apparatus is obvious. 



Another and very great advantage of it is this, that 

 in a dark room an object may be exhibited to several 

 persons at once. It would be very convenient for 

 class demonstrations. 



I have no doubt that, for drawing objects in the 

 way I have described, the Oxyhydrogen Lantern 

 Microscope, mentioned on page 229 of Davis's 

 " Practical Microscopy," and sold by Mr. Browning, 

 complete with objectives, but without lantern, for 

 ,£5 ios., would be very useful, and certainly better 

 for class demonstration. Mr. Davis says that for 

 exhibition neither oil nor the best paraffin-lamps 

 yield enough light. The electric light would do if a 

 larger lamp were used, and possibly for drawing 

 merely, less powerful lights. 



I have only just seen the series of articles on 

 "Drawings, &c, from the Microscope " in Science- 

 Gossip for 1882, pages 1, 39, 49, 74, 90, 97, 230. 

 Mr. Draper remarks on page 1 : " The effect of a 

 microscopical painting is greatly enhanced by its 

 being drawn within a circle, surrounded by a black 

 margin forming a square." I think it would be much 

 the best plan to buy paper with the black square and 

 white circle in centre, ready lithographed, from 

 Messrs. Watson & Sons, High Holborn, who 

 execute the plates for Cole's " Studies in Micro- 

 scopical Science." 



In Februrary 1882, page 39, [Mr. Holmes remarks : 

 " E. T. D. omitted to notice that outlines produced 

 by camera-lucida are reversed." In reply to this 

 remark, Mr. Draper, in April, page 74, says : " The 

 neutral tint reflector . . . has the great disadvantage 

 that everything is reversed ; consequently, when 

 removed, any further drawing from the microscope 

 is extremely difficult, not to say impossible." He 

 says further : "I am persuaded this neutral glass 

 reflector has often been a snare and delusion to many 

 a young draftsman, and should at once be abandoned 

 by those who are ambitious to do prolonged after 

 work." This is a good instance of the danger of 

 hastily condemning appliances which happen to 

 differ from those of which one habitually makes use. 

 It is perfectly obvious that nothing further is required 

 than a semi-rotation of the stage, to place the object 

 the other way up, and enable one to fill in details. 

 Of course the light and shade require attention, but 

 the larger structural detail could be filled in. 



In March, on page 49, Mr. Suffolk says: "I 

 dispense entirely with camera-lucida, and substitute 

 a grating ruled in squares ... on a double convex 

 lens. The drawing is made on ruled paper." In 

 May Mr. Draper, page 97, comments on this, that 



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