Progress of Invention. 235 



ROYAL GEOGRAPHICAL SOCIETY.— March 13. 



Ox Stereoscopic Maps of Mountainous Countries. — Messrs. 

 Galton described a new application of photography to the delinea- 

 tion of monntainons districts, whereby stereoscopic slides of the 

 ordinary size could be printed for the nse of tourists. The best 

 maps fail to impart a correct idea of the inequalities of mountainous 

 regions ; this can be done only by models in relief, which are, of 

 course, too cumbersome to be of use in travelling. By taking 

 stereoscopic views of good models (previously coated temporarily 

 with white paint), and giving an index of names of places on the 

 back of each slide, referring to numbers on the stereoscope, all the 

 advantages of a model could be given in a portable form, which 

 could be viewed with a common eye-glass stereoscope, to be carried 

 in the waistcoat pocket. In the case of models representing a 

 large area they could be divided into squares, and separate stereo- 

 graphs taken of each division. This method offers great advantages 

 for the illustrations of guide books of mountainous districts. 



MANCHESTER PHILOSOPHICAL SOCIETY. 



Development of the Wings of Butterflies and Moths. — An 

 interesting paper was read by Mr. Sidebotham on the great and rapid 

 increase in the size of the wings of Lepidopterous insects immediately 

 after they emerge from the chrysalis. This increase is caused by air, 

 which is taken in through the spiracles or breathing pores, and sent 

 into the vessels of the wings. By this means the membrane is 

 expanded, and the scales which were previously packed under each 

 other as closely as possible are forced . to slide out, until they are 

 arranged in the same manner as the scales of a fish or the tiles on a 

 roof. The wing of a moth in an unexpanded state, before it has 

 emerged from the chrysalis, is not folded, but lies perfectly flat ; and 

 all the markings can be seen in miniature as indicated by the edges 

 of the scales, which are then alone visible. 



PROGRESS OF INVENTION. 



Adaptation of Photography to Wood Engraving. — Among the 

 numerous advantages derived from photography, none is of greater 

 importance than the assistance which it affords to the artist. But 

 its uses, in this respect, have been greatly circumscribed by the fact 

 that, hitherto, it has been almost impossible to avoid the necessity 

 of transferring the picture, by the tedious and necessarily imperfect 

 means of the pencil, to the wood on which the designs are to be 

 reproduced. There is no difficulty in obtaining the photograph on 

 the wood itself; but, unfortunately," in doing so, the nitrate of silver 

 employed disorganizes it, and destroys its most valuable properties. 

 A varnish may, it is true, be used to protect the wood ; but then it, 

 is difficult, if not impossible, for the engraver to perform his part of 

 the process with delicacy and effect. The use of the Wortliley type, 



