June 14, 1907] 



SCIENCE 



937 



knowledge of tlie subject gives authority to Ms 

 estimate of the value of the future air-ship in 

 vparfare. 



The remainder of the book is mainly devoted 

 to dynamical aeronautics. Professor Miillen- 

 hofl analyzes briefly the principles of animal 

 flight in Chapter X., and in the first part of 

 the nest one. Major Moedebeck gives the his- 

 tory of man's attempts at flight. In the same 

 chapter a paper by the late Otto Lilienthal on 

 artificial flight is followed by Mr. Chanute's 

 account of the modem experiments where one 

 looks in vain for any mention of the remark- 

 able machines of the late Professor Langley. 

 In Chapter XII. Major Moedebeck describes 

 the air-ship or motor-balloon, in the list of 

 whose performances, by some error, the drift- 

 ing race of spherical balloons in 1906 for the 

 Gordon-Bennett cup has been included, with 

 the name of the winner strangely distorted. 

 The next three chapters, on flying-machines, 

 their motors and screws, are by the well-known 

 Austrian expert. Major Hoernes. Chapter 

 XVI., the last one, contains a convenient list 

 of the aeronautical societies of the world and 

 an appendix has a useful collection of tables 

 and formulae. The index is inadequate to so 

 much material, but, in spite of this and some 

 minor defects, the work can be highly recom- 

 mended to the increasing number of persons 

 interested in the investigation or navigation 

 of the air, as the best existing treatise on this 

 rapidly-developing subject. 



A. Lawrence Eotch 

 Blue Hm Meteobological Obsebvatoet 



SOCIETIES AVD ACADEMIES 



THE AMERICAN CHEMICAL SOCIETT. NORTH- 

 EASTERN SECTION 



The seventy-seventh r^ular meeting of the 

 section was held at the State Mutual Eestau- 

 rant, "Worcester, Mass., on May 18, at seven 

 o'clock P.M. The paper of the evening was 

 upon ' Ceramics,' by Dr. Frederic Bonnet, Jr. 

 The speaker first referred to the importance of 

 the clay-making industry, it being the third 

 in magnitude and only surpassed by those of 

 coal and iron. The value of clay products in 

 1905 reached the immense sum of $145,697,- 



188. Of this, brick represent nearly one half^ 

 Clay consists of naturally occurring earthy 

 materials having more or less plasticity when- 

 wet, and which, when heated to redness or 

 higher, becomes hard and rocklike. Clays are 

 of secondary origin, and are the product of 

 the decomposition of feldspathic or serpentine 

 rocks. Brongniart, and also Dr. Cushman, of 

 the U. S. Department of Agriculture, testing 

 laboratory for road materials, have made re- 

 searches which indicate that the decomposi- 

 tion of the feldspar is a kind of electrolysis, in 

 which the alkali constituent passes into solu- 

 tion, leaving the alumina and silica. The- 

 noted deposits of Cornwall, England, Zettlitz 

 in Bohemia and certain deposits in Germany,, 

 however, appear to have resulted from the ac- 

 tion of acid vapors on feldspar. Deposits 

 formed by weathering are usually shallow and 

 the original feldspar is found beneath. True 

 kaolin is formed from feldspar and is essen- 

 tially a basic hydrated aluminum silicate. If 

 the clay has been transported by water and' 

 again deposited, it usually contains some im- 

 purities; if little iron is present and the clay- 

 is tough and plastic, it is called ball clay. The 

 cause of plasticity is not fully understood 

 and no entirely satisfactory theory has been 

 advanced. One of the most recent, the colloid 

 theory, fails to meet the case and does not 

 explain the cohesiveness of a ball clay. The 

 history of pottery is, to some extent, the his- 

 tory of man; from the crude pots of primitive 

 races to the decorative ware and porcelain of 

 advanced civilization. Clay is often used just 

 as it is found for brick, tile and common pot- 

 tery, but for aU better ware it needs selection 

 and preparation. In the finest ware and for 

 some special purposes, it is subjected to very 

 fine grinding and mixing, or long tempering 

 and ageing. The effect of silica on the fusion 

 point of clay is very important; pure kaolin, 

 fuses at temperatures about 1,800° C, or 

 higher, but free silica lowers this, and hence 

 should not be present in too great an amount 

 in fire-clays. But metallic oxides are the 

 most noticeable fluxes in clays; the fusion 

 point decreases as the percentage of bases 

 rises. But the bases exert this depressing 

 effect on the fusion point in proportion to. 



