cxxiv GENERAL SUMMARY OF SCIENTIFIC AND 



by streams of steam passing from a boiler, with a pressure of 

 seventy pounds to the square inch, through orifices in a phite, 

 before which revolves another plate having corresponding 

 lioles, so as alternately to interrupt and permit the flow of 

 steam. This instrument has been constructed, under the 

 auspices of the Light-house Board, by Messrs. Brown, of New 

 York, and has lately been highly approved by Professor Tyn- 

 dall in a report to the British Trinity Board. 



TECHNOLOGY, 



In Technology^ the past year produced no remarkable or 

 revolutionizing inventions, but numerous advances in various 

 arts by the introduction of improved machinery and methods 

 are noticeable in many directions. 



In the operation and control of railway trains, both in the 

 United States and abroad (though to a greater extent with 

 us), great improvements have been made within the year. 

 These arise from tlie very great interest lately taken by the 

 managers of railroads in improved methods of braking and 

 switching trains. The substitution of 230wer-brakes for the 

 hand-brakes has become very general upon American rail- 

 roads, especially upon the Eastern roads. The principle upon 

 which these improved appliances operate is either with com- 

 pressed air, as in the Westinghouse ; with vacuum, as in the 

 Smith ; or with water pressure, as in the Henderson and oth- 

 er forms of hydraulic brakes. 'The interest which this sub- 

 ject is attracting among railway managers is evidenced by 

 the fact that at the recent meetino; of the American Raihvav 

 Master Mechanics' Association, where this subject attracted 

 much discussion, the opinion was unanimously expressed that, 

 in view of the security and certainty with which they joer- 

 mitted the trains to be controlled, the several forms of con- 

 tinuous power-brakes were infinitely to be preferred to the 

 hand-brake. The last year likewise witnessed the introduc- 

 tion of the air-brake upon the English roads, where it has 

 met with great success and popular approval. The increas- 

 ino; interest manifested on all sides in securino; additional 

 safety in railway travel, and the notable improvement in the 

 mechanical devices to eftect this object, are matters of con- 

 gratulation. 



The subject of eflTectiiig some mode of transit in large cit- 



