606 



SCIENCE. 



[Vol. I., No. 21. 



become the best standai'd among European 

 makers. 



Among the hot-air engines, that of Rider is 

 given a leading place, and is fully described. 

 It is commended for its simplicitj', its quiet- 

 ness in action, its regularity, and its careful 

 design. 



S tow's flexible shafting is noticed as one of 

 the characteristic products of American inge- 

 nuity. It consists of two oppositely twisted 

 helices of steel wire, the one enclosing the 

 other, and both covered with a flexible sheath. 

 The device is recommended for the transmis- 

 sion of motion around a corner. These Amer- 

 ican exhibits were all properly commended in 

 the award of premiums by the jurj-. 



Among other important exhibits from Euro- 

 pean countries were various forms of ' safet}'- 

 boilers ; ' the singular modification of the 

 injector of Giffard, which, by means of tlie 

 energj- of the exhaust-steam, performs the func- 

 tions of the air-pump in the steam-engine ; 

 several forms of compound engine ; Hall's pul- 

 someter, which is a modification of the Saverj^ 

 steam-engine of nearly two hundred 3'ears ago, 

 with automaticallj' working valves, — an Amer- 

 ican invention ; the gas-engine of Otto, which 

 is said to have exceptional efficiencj' ; the 

 Sagebien vertical water-wheel, which is claimed 

 to have extraordinary performance ; the indi- 

 cator of Deprez, which gives a diagram from 

 the fastest engines ; and manj' other important 

 inventions. 



One remarkable feature of the exhibition was 

 the absence of valueless and eccentric devices. 

 This point of diflference, in contrasting the 

 exhibition with those which preceded it, is 

 attributed largely to the progress of technical 

 education. 



In studjing progress, it is noted that the 

 gain is considerable in everj- direction. In the 

 production of steam, the more general use of 

 ' heaters ' of the feed-water is observable, the 

 use of tubular and of the ' safetj- ' forms of 

 boiler is increasing, superheating is oftener 

 practised, better material and workmanship 

 are seen. In steam-engine practice, the use 

 of higher steam, of greater expansion, the 

 adoption of two tj-pes exclusively, — -the com- 

 pound of the Woltf type, and the American 

 forms of single-cylinder engines, — greater 

 speed of piston and of rotation, and the use of 

 better material and superior workmanship, are 

 the characteristics of recent practice. Rotary 

 engines are given up. Air and gas engines 

 are extensively used, but only for small powers. 

 Among the hydraulic motors, the turbines are 

 principallj- used, and have attained great per- 



fection in practice as in theory. Aerostation 

 has made no great progress, notwithstanding 

 the interest which it continually awakens. 



American exhibiters distinguished them- 

 selves by the boldness and the ingenuitj* of 

 their designs, and bj- their entire independence 

 of tradition. Their devices are adapted pre- 

 ciselj' and effectively to their work. " Les 

 Americains s' attachment avec inergie d, Vidie 

 premiere, d, I'idee juste; Us VamiUoraient, la 

 perfectionnaient, et, m&me au prix de grandes 

 complications de mechanisme, Us finissaient 

 par la faire triompher, et par I'lmposer de 

 nouveau c1 I'Europe." 



MINOR BOOK NOTICES. 



Conversion-tables of metric and British or United 

 States weights and measures, with an introduction. 

 By Robert H. Thurston, A.M., C.E. New 

 York, John Wiley §- Sons, 1883. 83 p. 8°. 



In the introduction, the requirements of any 

 S3-stem of weights and measures are given. 

 There is a brief history of the English and 

 French sj'stems, and the supposed advantages 

 of the metric are stated. The difficulties and 

 annoj'ances arising during the change from the 

 English yard and pound to the metre and 

 gram are suggested as sufficient reason for 

 this book. In the second part, containing the 

 tables of conversion, the units of length, mass, 

 stress, work, and heat, temperature and baro- 

 metric pressure are defined. A chapter is 

 devoted to c. g. s. units. The tables are full, 

 numerous, and seem to be well arranged, and 

 will, without doubt, be found useful by those 

 having occasion to make measurements. This 

 book forms part of a treatise, in three volumes, 

 on the Materials of engineering, by the same 

 author. 



How the great prevailing winds and ocean-currents are 

 produced, and hoio they affect the teviperature and 



dimensity of lands and seas. By C. A. M. Taber. 



Boston, Wi'ffiams, 1882. 82 p. 12°. 



This pamphlet, by Capt. Taber of Wakefield, 

 Mass., gives a practical seaman's views on the 

 origin of winds and ocean-currents, and sug- 

 gests certain very hj'pothetical causes for gla- 

 cial climate. The fundamental errors of the 

 work lie in a misconception of the sun's action 

 in producing, and the earth's eflfect in deflect- 

 ing, the winds, and in a tendenc}^ to refer 

 apparently simple efl^ects to single instead of 

 composite causes. The other side of some 

 of the questions here raised is presented in 

 Tchiatcheft"s or RoUand's descriptions of the 

 Sahara, and Woeikoff's and Hann's articles 

 on the general atmospheric circulation. 



