1052 Tjjaxsacttoa'^s of the American Institute. 



change in the density of the air in the case to which the alarm is 

 attached, and thus set it off. 



The tubes are provided inside with small steel rods left free to 

 roll, if an attempt should he made to saw the grating. 



The door of a safe mav be provided with a conducting tube, the 

 end of which is closed by a valve attached to the door, either outside 

 or inside. 



Any partial opening of the door allows the air in the tube to start 

 the alarm. Several alanns on several doors or gratings may be con- 

 nected with a single connecting tube, and all the alarms be set in 

 action by any tampering with any part of the arrangement. In the 

 jail at Portland, this invention has been in use two years, and the 

 sheriff and United States marshal pronounce it " the only prison 

 grating in which perfect security is obtained." 



Railway ackoss the Appenines. 



Mr. J. Johnson exhibited and described a map showing the line of 

 the railway across the Appenines in Italy, extending from Bologna 

 to Florence, and built to establish direct communication between 

 North Italy and Tuscany. This railway is located in the mountain- 

 ous region along the river Reno, and is remarkable for the engineer- 

 ing difficulties overcome in its construction. 



Between Bologna and Pracchia, this latter the most elevated station 

 along the line, and two thousand feet above the level of the sea, the 

 Reno is crossed nineteen times by bridges, and twenty-three tunnels 

 have been dug, having an aggregate length of five miles. Between 

 this point and Florence are not less than fourteen tunnels and many 

 viaducts, and at the Florence end of the road the latter is returned 

 or doubled upon itself three times in order to enable the trains to 

 gradimlly make tlie steep incline. 



In a distance of fifty miles, there are twenty -three (23) bridges and 

 forty-five tunnels, wliich vary in length from a few hundred feet to 

 over 9,000 feet. At the point where the railway reaches the plain, 

 it is 2,000 feet above the level of the surrounding country, and 

 descends by a very circuitous zigzag track. Mr. Johnson derived 

 most of his facts from a pamphlet published by Mr. Cook, who in 

 1858 escorted a party of one hundred persons through most of the 

 remarkable scenery of Europe. As the travelers formed a somewhat 

 numerous party, they were enabled to contract for board-bills, &c., 

 at very reduced rates. 



