10 



POPULAR SCIENCE ISTEWS. 



[January, 1888. 



panj-ing engravings. One is engraved with a 

 number of human faces, some of which are 

 drawn with small horns on the forehead ; 

 another has only one face, quite deeply cut ; 

 another has a sort of scale divided into six- 



teen parts ; while the fourth stone, which is 

 not illustrated, is marked with two crosses, 

 very much defaced, and a kind of horizontal 

 cartouche rounded at the extremities and 

 divided into eight parts. The horns with 

 which the human faces in Fig. 2 are drawn, 

 recall to mind the passages in the Bible where 

 the " horn of the 

 righteous " is re- 

 ferred to. 



The significance of 

 these markings is 

 unknown ; but the 

 depressions, circles, 

 crosses, and gradu- 

 ated scales bear a 

 curious resemblance 

 to the marking on 

 certain prehistoric 

 dolmens in France 

 and England, nota- 

 bly' one near Plou- 

 harnel in Brittany. 

 Their age is uncer- 

 tain. They doubt- 

 less belong to the 

 neolithic or polished-stone age, as is shown by 

 the numerous stone implements and weapons 

 found near them ; but there is no means of 

 knowing how long ago that epoch occurred 

 on the isthmus, although it was man}' years 

 probably before the time when the wonderful 



mens of ancient pottery, both domestic and 

 votive, are constantly being discovered. The 

 illustration (Fig. 6) is taken from a photo- 

 graph of some of the finest examples, which 

 resemble in some respects the pottery from 

 Cj-prus in the collection of the New York 

 Metropolitan Museum, as well as some speci- 

 mens of Etruscan origin. 



We do not think that the resemblance be- 

 tween either the rock-markings or the pottery 

 of the western and eastern hemispheres is a 

 matter of very great significance, as indicating 

 that they were the work of the same race of 

 men. Certain forms, like the circle or the 

 graduated scale, are common to the under- 

 standing of mankind in general ; and the pot- 

 tery of a rude and unskilful people in any part 

 of the world would have many points of re- 

 semblance from the verj- nature of the case. 

 Still, a connection between the Old and New 

 World in times long before the' discoveries of 

 Columbus, is not an impossibilitj-. Future 

 explorations in Mexico and Central America 

 maj- shed new light on the question, and give 



covered or draped with perfectly black paper 

 or cloth. When all is readj-, the door is 

 opened, and in the centre of the stage is seen 

 a plaster or pasteboard head (Fig. 1). The 



Fig. 4. 



buildings and monuments of Mexico and 

 Yucatan were erected. This ancient civiliza- 

 tion never flourished on the Isthmus, but was 

 confined to the countries to the north and 

 south. No ancient ruins or burial places 

 have been found in the region adjoining the 

 Panama Canal. 



Farther to the north, near Cheriqui, speci- 



us more certain knowledge as to how the 

 American continent was originally peopled. 



THE DISSOLVING SPECTRE. 



A CURIOUS OPTICAI. ILLUSION. 



A WRITER in a recent number of La Nature 

 describes a most ingenious and beautiful opti- 

 cal illusion, which requires no apparatus except 



Fia. 1. 



a piece of plate-glass, and can be performed 

 by any one for a winter evening's amusement. 

 A small stage is improvised in a doorway' 

 between two adjoining rooms. The opening 

 facing the audience should be from one to two 

 feet square, and all parts of the stage must be 



exhibiter takes it up and passes it round 

 among the audience, and then returns it to its 

 place. It immediately begins to take on a 

 lifelike expression : the eyes open, the lips 

 smile ; and in a few moments the inanimate 

 figure is transformed 

 to a living human 

 head, which even 

 speaks or sings. 

 This begins shortly 

 to fade awa}', and is 

 transformed into a 

 cabbage, which in 

 turn is replaced by 

 an empty dish which 

 becomes filled with 

 fruit or flowers, which 

 are passed round 

 among the audience. 

 On restoring the dish 

 to its place, it passes 

 through numerous 

 other transforma- 

 tions, ending finally 

 in the original plaster cast. 



The accompanying diagram (Fig. 2) ex- 

 plains the simple means bj- which these puz- 

 zling eflTects are produced. The line NMAD 

 represents the front part of the miniature 

 stage, at the back of which is a table, AMEO. 

 Placed diagonally across the stage at AB is 

 a piece of plate-glass which completely fills 

 the opening. At P is placed the plaster bust, 

 and at F the living head into which it is 

 to be transformed, the rest of the bod}- being 

 concealed. Two lamps or gaslights are ar- 

 ranged so as to strongly illuminate the objects 

 alternately. 



At the beginning the back part of the stage 

 is illuminated, while the side at F is in dark- 

 ness. The light from the object at P passes 

 directly through the glass, which is not visible ; 

 and the bust is in full view of the audience. 

 Then, if the light at P is slowly turned down 

 while that at i^is raised, the artificial bust will 

 appear to transform itself into the living head ; 

 the sheet of glass now acting as a mirror, and 

 reflecting the image of the object at F towards 

 the spectators. Meanwhile an assistant has 

 placed the cabbage or other object at P; and 



