140 



THE POPULAR SCIENCE MONTHLY 



The Wcstinghonse Aatomatic Brake. 



The well-known Westinghouse air-brake, in- 

 vented and so largely used in this country, 

 seems to be rapidly gaining in favor abroad. 

 The English journal " Iron," in a recent is- 

 sue, highly commends it as answering all 

 the requirements of a perfect brake, as laid 

 down by the Board of Trade, and gives some 

 valuable statistics concerning its use. Fi'om 

 returns received up to the 20th of last July, 

 it appears that the number of applications 

 of the automatic brake throughout the world 

 is to engmes, 3,277, and to carriages, 13,- 

 502. This is an increase in less than four- 

 teen months of 1,594 to engines, and 6,255 

 to carriages. Besides this, there are 2,472 en- 

 gines and 8,812 carriages fitted with the non- 

 automatic brake that is, the one using ordi- 

 nary air-pressure. This, then, makes a total 

 of 5,749 engines and 22,314 carriages fitted 

 with this apparatus. In the case of 678 

 engines and 2,720 cars a change has been 

 made from the non-automatic to the auto- 

 matic. This equipment is divided between 

 the different countries as follows : The Uni- 

 ted States has 2,211 engines and 7,224 cars 

 using it ; England 456 engines and 2,942 car- 

 riages ; in France there are but 203 engines 

 and 1,609 carriages; and in Belgium 197 of 

 the foi-mer and 1,241 of the latter. The num- 

 ber in use in Germany, Russia, and Holland 

 is small, ranging from 55 to 28 engines and 

 93 to 117 carriage equipments. A few are 

 also in use in Italy, Sweden, and the British 

 provinces. Certain very excellent improve- 

 ments and additions " Iron " points out have 

 recently been made to this brake system, 

 which greatly increase its usefulness. There 

 are amethod of lighting the cars and a means 

 of communication with the engineer by the 

 passengers. The light is produced by carbu- 

 retting air in a manner somewhat similar to 

 that in common use in the numerous port- 

 able gas-machines. The air is reduced from 

 the high pressure necessary to operate the 

 brakes to a moderate and steady one. It is 

 then passed into a small iron box containing 

 sponges saturated with gasolene, and from 

 these passes to the burners. The light is 

 said to be of good quality and sufficiently 

 bright to see to read fine print in any part 

 of the car. Its cost is much less than gas 

 or any other material commonly used for 

 this purpose on railroads. The communi- 



cating apparatus consists of an arrangement 

 of air connections, such that the pulling of 

 a handle in the car starts a whistle on the 

 engine and on the car, and puts the brakes 

 partially on. The attention of the engineer 

 being attracted, he can complete the appli- 

 cation of the brakes if he is in a favorable 

 position for stopping, or, if not, release them. 

 The handle once pulled, the pass}ger can 

 not return it to its place. This can only be 

 done by one of the trainmen, so that im- 

 proper use of the apparatus is readily de- 

 tected. This appliance is especially designed 

 to meet the requirements of passengers in 

 the compartment carriages, such as are used 

 abroad. With the American system of cars, 

 the bell-rope furnishes a ready means of 

 communication, while the trainmen are gen- 

 erally within easy call. The lighting and 

 communicating apparatus can be added to 

 carriages after the brake is put in, and but 

 one connection between the carriages is re- 

 quired. 



The Circulation of Sap in Trees. Pro- 

 fessor Joseph B5hm has suggested, as a 

 theory to account for the circulation of the 

 sap in plants, that the exhaustion of the 

 water by evaporation from the top of the 

 plant causes a difference in pressure in the 

 adjoining cells, which produces a sucking up 

 of the fluid from the cells that are relatively 

 rich to those that are relatively poor in 

 water. He has also endeavored to make 

 clear what is the purpose of those vessels 

 which run the whole length of deciduous 

 trees, and which can be easily perceived 

 with the naked eye in sections of many spe- 

 cies, as the oaks, maples, etc. Generally 

 these vessels have been regarded as air- 

 vessels, but Professor Bohm has been con- 

 vinced that in many plants they not only 

 receive sap by measured transpiration, but 

 also in consequence of an active exhalation 

 take up a relatively great quantity of water, 

 so that the air fails to penetrate them at the 

 ordinary pressure and only escapes in con- 

 siderable quantities after the plant has be- 

 come drier. It has also been shown that 

 the branches of many plants, willows for in- 

 stance, notwithstanding their vessels are 

 supplied with fluid, are able to take up more 

 water from without, and in such quantities 

 that twigs will increase in weight twenty 



