80 . ANNUAL OF SCIENTIFIC DISCOVERY. 



before the plunger, it is evident that the plunger is driven with atmos- 

 phere pressure at the rate that air rushes into a vacuum, barring the 

 loss of velocity by friction. In all the atmospheric telegraphs heretofore 

 proposed, the motion of a long column of air behind the ball or carriage 

 has presented an insuperable obstacle to its operation on a long line. To 

 obviate the evil of Avorkino; on a long column of air behind the piston, 

 new air is admitted at different stations along the line behind the 

 plunger, and the long column is cut off so that the action is like a suc- 

 cession of short effectual efforts. This is done in an ingenious manner, 

 by valves hanging in the main tube connected with the atmosphere, 

 which are acted upon by the plunger as it rushes through the tube, 

 when the air is cut off a short distance behind the plunger, and a new 

 column commences to act, to force the carriage through. This propel- 

 ing power is so great as to produce an apparently instantaneous motion 

 of the plunger with its load from one end to the other of the model 

 tube on exhibition, Avhich is about 30 feet long and 1 ^ inch in diameter ; 

 indeed the plunger issues forth with so much force, when not confined, 

 as to knock down violently a heavy billet of wood placed opposite the 

 end of the tube, if it is left open. The speed is estimated at about 

 1000 miles in an hour. The apparatus is so arranged that there can 

 be intermediate stations upon the line, at which the progress of the 

 plunger can be arrested, or, if preferred, it can pass directly through 

 to the terminus. The inconvenience of the sudden shock occasioned 

 by the arrival of the plunger at the end of its journey is avoided by 

 an arrangement by which a portion of the air in front of it is com- 

 pressed and allowed to escape, but gradually, forming a sort of cushion 

 to ease the jolt. 



For the purpose of carrying the above described invention into 

 effect, it is proposed to build a line of atmospheric telegraph 2 feet in 

 diameter, from Boston to New York, for the conveyance of letters 

 and packages to and from the said cities and intermediate places, 

 allowing fifteen minutes for each transit; sending from Boston to New 

 York at every hour, and from New York to Boston at half-past every 

 hour, twelve hours each day. The cost of laying it down is estimated 

 at $2,000 per mile. There will be supply valves as often as once in 

 25 miles, and intermediate stations at suitable points ; for instance, at 

 Worcester, Springfield, &c. There will be air pumps at all the sta- 

 tions. 



SMOKE CONSUMING FURNACE. 



The London Mining Journal describes and praises very highly a 

 smokeless furnace, invented and patented by Mr. John Lee Stevens. 

 The invention consists in the combination of two sets of fixed fire- 

 bars, the first of which is chiefly fed by the scoria and cinders voided 

 from the second or upper set of fire-bars, with a caloric plate, the 

 face of which may be protected by a few fire-bricks ; by which arrange- 

 ment the current of air entering at the lower part of the furnace 

 passes through two strata of fire, and thence between the caloric 



