MICROSCOPE-TABLE. — LIGHT. 130 



the way when the Microscope is in use. Similar but smaller bell- 

 glasses (wine-glasses whose stems have been broken answer very- 

 well) are also useful for the protection of objects which are in 

 course of being examined or prepared, and which it is desirable 

 to seclude from dust. — For the purpose of Demonstration in the 

 Lecture Room, a small traversing Platform may be constructed to 

 run easily upon rollers, and to carry the Microscope and Lamp 

 securely clamped down upon it, so as to be passed from one^observer 

 to another. For Demonstration to a small party sitting round a 

 circular table, it is convenient to employ a A-shaped platform, the 

 vertical angle of which is pivoted to a weight placed in the centre 

 of the table, whilst the angles at the base are supported upon 

 castors, so that the platform may run round to each observer in 

 succession. Or the table itself, if not too large, may be made to 

 rotate (like a dumb-waiter) upon its central pillar. 



104. Light. — Whatever may be the purposes to which the Micro- 

 scope is applied, it is a matter of the first importance to secure 

 a pure and adequate Illumination. For the examination of the 

 greater proportion of objects, good daylight is to be preferred to 

 any other kind of light ; but good lamplight is preferable to bad 

 daylight. When Daylight is employed, the Microscope should be 

 placed near a window, whose aspect should be (as nearly as may be 

 convenient) opposite to the side on which the sun is shining ; for 

 the light of the sun reflected from a bright cloud is that which the 

 experienced Microscopist will almost always prefer, the rays pro- 

 ceeding from a cloudless blue sky being by no means so well fitted 

 for his purpose, and the dull lurid reflection of a dark cloud being 

 the worst of all. The direct rays of the sun are far too powerful 

 to be used with advantage, unless its intensity be moderated, 

 either by reflection from a plaster-of-Paris or some other ' white- 

 cloud ' mirror (§ 87), or by passage through some medium which 

 stops a greater or less proportion of its rays. This may be done 

 by placing coloured glasses over the eye-pieces, as recommended by 

 Mr. Wenham ; or by placing the ' moderator' specially contrived 

 by Mr. Rainey for lamp or gaslight illumination (§ 105) between 

 the window and the mirror. The young Microscopist is earnestly 

 recommended to make as much use of daylight as possible ; not 

 only because, in a large number of cases the view of the object 

 which it affords is more satisfactory than that which can be 

 obtained by any kind of lamplight, but also because it is much 

 less trying to the eyes. So great, indeed, is the difference between 

 the two in this respect, that there are many who find themselves 

 unable to carry on their observations for any length of time by 

 Lamplight, although they experience neither fatigue nor strain 

 from many hours continuous work by Daylight. 



105. When recourse is had to Artificial light, it is of great im- 

 portance, not only that it should be of good quality, but that the 

 arrangement for furnishing it should be suitable to the special 



