The Art of projection and complete magic lantern ... - Yesterday Image

ii8absorbed or lost by this piece of apparatus but the result is verybeautiful, and the object is shown in its true form, which often does nothappen when the pencil of light is passed directly through it.The markings upon many of the diatomacte can only bemade out orproperly determined when examined by oblique light, as procured byintercepting the central rays, which effect is produced by the spot lens.Objects, such as rocks, metals, etc., mounted upon the slide opaquely, orfor the determination of pigment-granules, cells, etc., will need aLIEBERKUHNwhich consists of a silver cup of such a curvature suited to the objectglass upon which it is to be used, and is fitted by sliding on to thebody or cell of object glass. The interior or front combination of samepassing through the centre of cup (except in the case of very deeplieberkuhns which are very rarely used). The light passing through thesubstage condenser and round the black disc upon which the object ismounted, is collected by this cup or curve and reflected back upon theobject from which it is taken up by the object glass and projected uponthe screen, giving back a brilliantly illuminated object upon a blackground.LIVEBOX.This piece of apparatus consists of metal base-piece upon which ais fitted having a glass bottom, into which slides another cell or tubealso having a glass fitted, this cell is provided with a moveable cap sothat the glass can be changed for varying substances suitable for theobject under investigation from ^^ to ^l^of an inch.The live box ismade to contain portions of liquid containing infusoriaand other small animals or plants can be confined so as to ]Dreventevaporation and allow of their being watched in a living state. Anotherpiece or apparatus specially useful for class work is theGROWINGSLIDEthe manner in which the slide is used is this ; supposing it is wished tofollow the changes undergone by some minute alga^cellor infusorium whichhas been detected in a drop of liquid, it is placed upon the slide,distilled water, mixed with a small proportion of the water in whichthe organism was living is next placed in the cup at side, ard a fewthreads of lamp wick cotton, thoroughly moistened with distilled water,are then so placed that one end is immersed in the cup whilst the otheris brought into contact with the edge of the liquid in which the object