86 ANNUAL OF SCIENTIFIC DISCOVERY. 



direction of the engineer corps of the French army, to ascertain, if it were 

 possible, to maintain a balloon five or six hundred metres above a fortified 

 town, and, if so, to cause incendiary or fulminating balls to fall. Nothing 

 was successful, and the commission, after the expenditure of much money, 

 gave up the project. 



FORMATION OF THE CHINESE CONCENTRIC IVORY BALLS. 



The Rev. TV. C. Milne, in his recent work on China, thus explains the 

 mystery of curved concentric ivory balls, ten, twelve, or more, cut oat, one 

 within the other : 



It has long puzzled people how so intricate a piece of workmanship is 

 fabricated. It has been conjectured, that originally they are balls cut into 

 halves, so strongly and nicely gummed or cemented together that it is 

 impossible to detect the junction. And I have seen it deliberately stated, 

 that attempts have been made by some to dissolve the union by soaking and 

 boiling a concentric ball in oil, of course, to no purpose. The plain solu- 

 tion, obtained by myself from more than one native artist, is the following : 

 A piece of ivory, made perfectly round, has several conical holes worked 

 into it, so that their several apices meet at the centre of the globular mass. 

 The workman then commences to detach the innermost sphere of all. This 

 is done by inserting a tool into each hole, with a point bent and very sharp. 

 That instrument is so arranged as to cut away or scrape the ivory through 

 each hole, at cqui-distances from the surface. The implement works away 

 at the bottom of each conical hole successively, until the incisions meet. In 

 this Avay the innermost ball is separated ; and to smooth, carve, and orna- 

 ment it, its various faces are, one after the other, brought opposite one of 

 the largest holes. The other balls, larger as they near the outer surface, are 

 each cut, wrought and polished precisely in the same manner. The outer- 

 most ball of course is done last of all. As for the utensils in this operation, 

 the size of the shaft of the tool, as well as of the bend at its point, depends on 

 the depth of each successive ball from the surface. Such is their mode of 

 carving one of the most delicate and labyrinthic specimens of workman- 

 ship to be found in China or elsewhere. These " wheels within wheels " arc 

 intended chiefly for sale to foreigners ; and numerous specimens annually 

 are sent to England and America. 



EXPERIMENTS ON IRON TARGETS. 



Some experiments have been made at TVoolwich, England, to test the 

 power of resistance of timber lined with four-inch iron plates ; the combined 

 materials being of the same thickness as the immense floating batteries con- 

 structed during the late war ; and also to test the durability and quality of 

 iron plates manufactured by rolling, as compared with iron turned out by 

 the hammer. The target was an immense construction of timber, lined 

 with four-inch plates of iron, of both descriptions, and the total weight was 

 thirty tons. This target was placed on a foundation constructed for the pur- 

 pose, and twenty-four rounds of 6S-poundcrs were fired, with the following 



