THE BOOK OF THE LANTERN. 13 



is to show certain preparations and other objects which 

 must be kept in a horizontal position during exhibition. 

 " Horizontal Attachment " would, therefore, perhaps be a 

 more sensible name for the apparatus the construction of 

 which can be easily understood by reference to the annexed 

 cut (fig. 7). The round opening in front, four inches in 

 diameter, is the place where the apparatus fits on to the 

 lantern, the lenses, &c., of the latter having been removed 

 for its accommodation. So that the light from the lantern is 

 received by the sloping mirror, and is reflected upwards 

 through a condensing lens, which is placed horizontally. 

 This lens forms a table or stage upon which different slides 

 or preparations can be laid for exhibition. The image is 

 formed by the lens above, and by the prism above that is 

 redirected and cast upon the sheet or screen. It is obvious 

 that some loss of light must result from filtering the rays 

 through so many media, but this cannot be helped. In 

 the chapter dealing with experiments possible with the 

 lantern the use of this vertical attachment will be further 

 alluded to, when its value will be better appreciated. 



Double lanterns to burn oil are usually placed side by 

 side, but fig. 8 shows a convenient form of lantern which 

 has been recently introduced, and which is so constructed 

 that one lantern can be detached from its fellow. Thus, 

 when the lime-light is used they are adjusted one above 

 the other, and when the oil lamp is employed they are 

 placed side by side. Mr. Tyler has still more simplified 

 the matter by inventing a biunial lantern which burns 

 oil, although the position of the two lamps is one above the 

 other. This he achieves by the use of a bent chimney, 



