SCIENCE. 



537 



the air, instead of being heated by a small boiler, was 

 made to pass through a tank which was supplied at in- 

 tervals with boiling water and recharged as soon as the 

 water cooled. The present arrangement is the result of 

 experience derived from its predecessor. 



The valve gear is simple and is fitted with a variable 

 expansion valve under the control of the engineer, by 

 which the cut-off can be varied from i-ioth to 5-8ths of 

 the stroke. The link is worked by "crossed" eccentric 

 rods, the effect of this being to prevent any opening of 

 the parts when the reversing lever stands in the middle 

 notch. By this arrangement the cylinders are, when ne- 

 cessary, converted into vacuum pumps and are utilized to 

 operate the vacuum brakes attached to the cars. It has 

 been found that when using the air expansively while 

 running, i. e., with a quiet " cut-off," the expansion is 

 sometimes so rapid that towards the end of the stroke the 

 pressure in the cylinders is less than the external atmos- 

 phere; to obviate the loss of power which would be 

 caused by the vacuum thus created, valves are placed in 

 the exhaust passages, which prevent any vacuum being 

 formed. Another feature in the engine is the existence 

 of a suction and delivery valve at each end of both 

 cylinders, which render it possible when going down hill, 

 or approaching a station, to convert the cylinders them- 

 selves into " compressors," by which the pressure in the 

 reservoirs can be increased, thus utilizing the waste 

 energy which is usually given off in friction against the 

 brakes. This arrangement is so successful that no other 

 brakes are required on the engine. There are several 

 minor points in the construction of the machine which it 

 is not necessary to mention here ; we may, however, say 

 in conclusion that the engine has been carefully studied 

 in every detail. 



At the trial, the engine started from 128th street 

 with a pressure in the reservoirs of 580 lbs. per inch, 

 and travelled as far as 42nd street, a distance of 4^ 

 miles or thereabouts, stopping at every station, and 

 loaded with three cars containing about 50 people. 

 At 42nd street some switching was done, and the engine 

 then returned to the starting place, reaching 128th street 

 with a remaining pressure of 115 lbs. 



These figures show that the train would have run from 

 Harlem to South Ferry, the entire route of the Elevated 

 Road. But in making any practical calculation, it must be 

 remembered that four cars are often used instead of 

 three, and that these four cars would often be loaded 

 with 5oo persons. This probably implies an additional 

 weight of about thirty tons to that placed behind the 

 Pheumatic Engine during the recent experiment. 



The company must be congratulated on building a 

 most successful engine. 



UNIVERSAL ENERGY OF LIGHT.* 

 By Pliny Earle Chase, LL. D., 



Professor of Philosophy in Haverford College. 



Force is generally regarded as a function of mass and 

 velocity. The greatest known velocities which can be 

 produced by central forces are wave velocities. The 

 greatest known wave-velocity which appears to be uni- 

 versally diffused is the velocity of light. 



Let vk = velocity of light ; ^ =circular-orbital velocity 

 at sun's surf ace = Vg„r ; 7/ 3 =Earth's mean orbital 

 velocity ; v r = velocity of Sun's equatorial rotation ; u 3 = 

 potential velocity of water at 0°C. =Jzgy. 100 x 1389.6 

 ft. ; Ui = potential velocity of water at its maximum 

 density ; « 6 =potential velocity of water-evaporation = 

 v 2fx 536.37 x 1389.6 ft. ; ttio, m 3 , m & , ;« 6 =masses of 

 Sun, Earth, Jupiter, Saturn ; /2 =Earth's semi-axis ma- 

 jor ; ^ 3 =height of mean oscillatory projection due to the 



* Read before the American Association for the Advancement ot Science, 

 August, 1881. 



combining energy of H 2 ; ^„=time of acquiring circu- 

 lar-orbital velocity at Laplace's limit of synchronous ro- 

 tation and revolution = time of rotation -s- 2 n ; l n = time 

 of acquiring " nascent " or dissociative velocity at nucleal 

 surface = y\ time of rotation = nt a \ ;v=Weber's electro- 

 chemical unit; ^electromagnetic unit; /> = total mag- 

 netic force; p 3 =terrestrial magnetic force; / = present 

 value of /„at Sun's surface ; < §- =gravitating acceleration 

 at sun's surface. 



The simplicity of the relations of the universal velocity 

 vk to other physical velocities, is shown in the following 



equations : 







1. 



vk 



- K _ 





Ui 





m 3 



2. 



vk 



Vo 



- v ° r 



— . V 2 



Ui 



_ t» 



3- 



go 



= U 





4- 



vk 

 v 3 



m 3 



m t a 

 m 3 t n 



5. 



v% 



_ 3 4 ^o 



_ 5 x 3 3 m 





Us 



2 W 6 



mt 



V. 



x 



The velocity of solar atmospheric rotation, at the secu- 

 lar mean centre of gravity of the solar system, is also 

 equivalent to Us,. 



The law of conservation of areas, in an expanding or 

 contracting nucleus, requires that g should vary in- 

 versely as t a . Equation 3 should, therefore, hold good 

 for all stages of solar existence, past, present and future. 



The values which satisfy the above equations are : 

 7/20 = 328470 m 3 ; ^0=92476500 miles ; vk — 185760 miles; 

 2/3 = 18.412 miles ; 2^ = 2986 ft. ; 2^6=6916.2 ft. 



The following table shows the accordance between 

 theoretical and observed values : 





Theoretical. 



Observed. 



Combining heat of H 2 



Pe 



99°. 18 

 69319 

 140.65 

 4°. 19 

 18.31 

 53 6 °-374 

 107.38 



IOO° 



67616 to 69584* 

 140 lb. pr. sq. in. 

 3°-33 to 4°.8s 

 18.41 

 536°. 385 t 

 106.67 



Maximum density of water. . . . 



v 3 — : 



*-ri" 





The velocity of light is also a factor of electromotive 

 energy. Weber and Kohlrausch demonstrated this fact 

 by measuring quantity of electricity ; Thomson and Max- 

 well, by measuring electromotive force ; Ayrton and 

 Perry, by measuring electrostatic capacity. 



Perhaps the most interesting of the above indications 

 is the past, present and future equivalence of Sun's 

 " nascent " velocity to the velocity of light ; the sum of 

 the cyclical reactions of solar superficial gravitation 

 against the actions of external gravitation, during each 

 half-rotation, being equivalent to the velocity of light. 



The Metal Actinium, by J. L. Phipson. — The 

 author stated that he had been a ble to separate a new 

 element from the pigment zinc-white. The oxide of the 

 new element is said to be slightly soluble in caustic soda, 

 and is soluble in ammonia and ammoniacal salts. Its 

 color is uninfluenced by exposure to light. The sulphide 

 of actinium is described as a pale yellow canary-colored 

 substance ; it is insoluble in ammonium sulphide, is solu- 

 ble in acetic acid, and becomes darker on exposure to the 

 air. — British Association, 1881. 



* The mean of six estimates, cited by Naumann, is 68886. 

 t This is the mean of four estimates, viz. : Kavre and Silbermann, 

 535°. 77; Andrews, 535°.qo, Regnault, 536". 67 ; Tyndall, 537°.20. 



