514 



SCIENCE, 



[Vol. VI., No. 149. 



economic method of automatically cutting off the 

 power with the governor is all that is necessary to 

 control the speed of the train, the brake rarely 

 coming into action. With steeper gradients, how- 

 ever, the brake would undoubtedly be very useful. 

 The way in which a single wheel-track is made 

 to serve for one train, or rather two wheel-tracks 



It is found that for moderate inclines direct 

 driving, with pitch chains, of two wheels with 



for two trains, instead of the necessity of having 

 four wheel-tracks for two trains, as in the ordi- 

 nary electric railways, is seen from fig. 4. D is 



Fig. 3. 



india-rubber treads, gives a gravitation grip suf- 

 ficiently large for satisfactory haulage. 



•.7 



M 



■»• 84 



'Bsi& 



T,^ 



L 



©1 



CiM 



^2» 



- ^^^-a 





B2' 



A, 



El 



[> 



Fig. 4. 



the dynamo maiutaining two long conductors 

 permanently at different potentials indicated by 

 the signs 4- and — of each section. The wheels 

 L and T of one train, and L^ and 1\ of the other, 

 are insulated from their trucks, and joined by a 

 conductor attached respectively to the terminals 

 of the motors M and M^, A current, consequently, 

 is always passing from a + section to a — section 

 through each motor. Mechanically, then, each 

 train is supported by what is practically one con- 

 tinuous steel rod ; but in reality at the tops of the 

 posts the rods are electrically subdivided into 

 sections, and joined across by insulated wires, one 

 of which may be seen at the top of the posts in 

 fig. 1. The wires connecting the two skeps with 

 the motor, shown in fig. 4, are not seen in fig. 1, 

 as they were too thin to appear in the photograph 

 from which this figure was taken. To prevent 

 the metallic wheels of the skeps short-circuiting 

 the two sections as they cross the tops of the 

 posts, there are insulated gap-pieces, which may 

 be seen m fig. 1, at the tops of the posts where 

 the steel rod is electrically divided. 



THE PRE-COLUMBIAN HISTORY OF GUA- 

 TEMALA. 



The well-known historian of Spanish America, 

 Antonio de Herrera, in describing the first con- 

 quest of Guatemala, states that the natives of the 

 province of Utlatlan had 'painted records,' which 

 carried their national chronicles back eight hun- 

 dred years, that is, to about the year 700 A.D. 



Utlatlan was the Mexican name of the region in 

 western Guatemala inhabited by the tribe called 

 Quiches, whose capital city, Gumarcaah, was de- 

 stroyed by Alvarado in 1524. Its ruins are still 

 plainly visible near the little village of Santa Cruz 

 del Quiche. So complete was the havoc of the 

 Spanish conquerors that not a single building was 

 left standing ; and, of those ' painted records ' re- 

 ferred to by the historian, not a shred is in exist- 

 ence. Fortunately for the antiquary, intelligent 

 members of the tribe learned to write their tongue 

 in characters devised for it by the early Spanish 

 missionaries, and took pains to apply this knowl- 

 edge to the preservation of their tribal traditions. 

 In some cases they had a practical incentive to this 



