MECHANICS AND USEFUL ARTS. 81 



Upon first entering, this view is limited to the southernmost parts 

 of Africa and America, magnified, in comparison with the delineations 

 of ordinary globes, to proportions almost beyond recognition. A^ stair- 

 case conducts to a zone where the central parts of these vast continents 

 are seen broadly expanded, and exhibiting the diversities of mountains 

 and valleys in bold relief, and of deserts and verdant plains, oceans, 

 lakes and rivers, represented as they might be supposed to appeal- 

 when seen from a great elevation. At the next ascent the spectator is 

 placed on the equinoctial line ; a gallery above corresponds in position 

 with the tropic of Cancer, and a still higher zone places in sight the 

 whole of Europe, and most of the civilized countries of the globe. ^The 

 higher the ascent the more interesting and more extended the view ; 

 and, by the time the spectator has arrived at the highest zone, he 

 becomes accustomed to the concave form, which, at first, is rather per- 

 plexing, as the exterior surface of the globe is seen from the interior. 

 There is no writing on the model ; the land is of as natural a tint as 

 possible to represent the temperature of the various zones, and the sea 

 is colored blue. The earth's form, as a whole, is shown; its general 

 aspect, the relative quantity and positions of its several parts, the 

 bearing of its hills, the flow of its great waters, and the seats of its 

 rich dales and barren wastes. The volcanoes are distinguished by their 

 fiery red tint ; and those mountains within the range of perpetual 

 snow are vividly represented in the frosty, glittering garments with 

 which nature clothes herself in these ice-bound regions. The relative 

 heights of the several mountains are given, and the course of the rivers 

 may be distinctly traced. The top of the globe is made the north pole, 

 and the bottom the south, without any regard being paid as to what is 

 known as the inclination of the ecliptic. The circular corridor, which 

 surrounds the lower part of the globe, is tastefully hung with maps and 

 charts of a most valuable description, and the walls and pillars deco- 

 rated in arabesque painting, being exact copies from some of the orna- 

 mental work in the Alhambra. 



FACTS IN RELATION TO THE TURBINE WHEEL. 



THE following is an abstract of a paper presented to the American 

 Association, Cincinnati, by Mr. J. Chase, of Mass., in relation to the 

 Turbine wheel : 



In computing the experiments which were made at Lowell, it was 

 found that when the gate was fully open, the quantity of water dis- 

 charged through the guides was 70 per cent, of the theoretical discharge. 

 The effect of the wheel during these experiments was 81^ per cent, of 

 the power expended ; but, when the gate was half open, the effect was 

 67 per cent, of the power, while the discharge through the guides was 

 11 per cent, more than the theoretical discharge. But, when the open- 

 ing of the gate was still further reduced to one fourth of the full opening, 

 the effect was also reduced to 45 per cent, of the power ; while the dis- 

 charging velocity was raised to 49 per cent, more than that given by 

 theory. In the first of these experiments the fall was 12 T 8 <y feet, in 

 the second ISy 2 ^ feet, and in the third IS^oir feet; and the 



