MISCELLANY. 



253 



rocks disintegrated in this way merely fall 

 to pieces, the hard portion remaining in the 

 shape of sand or pebbles. The transporta- 

 tion of this by streams produces what the 

 author calls corrasion. In this way the bed 

 of a stream is widened and deepened, but 

 the work is also facilitated by the ceaseless 

 action of water in dissolving the rocks. 



The mechanical wear or erosion by a 

 stream depends largely on its velocity. " A 

 stream of water flowing down its bed ex- 

 pends an amount of energy that may be 

 measured by the quantity of water and the 

 vertical distance through which it de- 

 scends." 



The velocity of a stream would continu- 

 ally increase if none of its energy was con- 

 sumed in friction, but very much of it is so 

 consumed, and reappears in innumerable 

 forms of movement or subsidiary currents. 

 It is by some of these that the work of 

 transportation and erosion is largely done. 

 Bat a stream may be overloaded with detri- 

 tus, and its corrading power correspond- 

 ingly diminished. " Only with a partial 

 load does a stream wear its bottom." Of 

 the Colorado plateau the author says that 

 the erosion which began with the first lift- 

 ing of a part above the ocean has progressed 

 continually to the present time. The total 

 uplift has been about 12,000 feet ; only 

 7,000 feet remains, that being the present 

 altitude above the level of the sea. Five 

 thousand feet of the general surface has 

 been removed, and an amount greater by 

 several thousand feet has been corraded by 

 the rivers. 



Improved Railway-Signal. A simple and 

 effective railroad-signal, in use on the Bos- 

 ton, Lowell & Nashua Railroad, is described 

 in the Scientific American. A single-cell Cal- 

 laud battery is connected to the two rails at 

 one end of a given section of the line say, 

 two miles in length each section being in- 

 sulated from adjoining sections. At the 

 other end the signal has an electro-magnet 

 similarly connected to the two rails. When 

 the circuit is closed, as is normally the case, 

 the magnet is excited and the signal con- 

 trolled thereby so as to show that the line 

 is clear. But, when a train runs on the 

 section, then a shorter circuit is made by 

 the wheels and axles, and the current re- 



turns to the battery by this course, instead 

 of passing through the signals. The mag- 

 net ceases to attract, and the signal by me- 

 chanical means is at once turned, to indi- 

 cate danger. It is obvious that this must 

 occur as long as a single car remains on the 

 track, or when the circuit is broken by a 

 displaced or ruptured rail or any other 

 cause. Hence the device may be applied 

 over an entire line, and will indicate the 

 condition of every section to a train about 

 to enter on the same. It is found to be 

 operative in all weathers. 



Powder-Paper. A substitute for gun- 

 powder has been invented in England, called 

 " powder-paper," viz., paper impregnated 

 with a mixture of potassic chlorate, nitrate, 

 prussiate, and chromate, powdered wood- 

 charcoal, and a little starch. The powder- 

 paper is rolled into the shape of a cartridge 

 of any required length or diameter. The 

 manufacture involves no danger, it is said ; 

 no explosion can take place except by way 

 of contact with fire. The powder-paper 

 leaves no greasy residue on the inside of the 

 gun ; it also produces less smoke, gives a 

 less violent recoil, and is less impaired by 

 humidity than gunpowder. With equal 

 charges, by weight, of gunpowder and pow- 

 der-paper, the penetrating power of the lat- 

 ter is T s g greater than that of the former. 



October Meteor-Shower. In a letter to 

 the Tribune, dated October 19th, Mr. Dan- 

 iel Kirkwood states that shooting-stars in 

 unusual abundance were observed by sev- 

 eral trustworthy witnesses at Bloomington, 

 Indiana, on the evening of the 18th, from six 

 hours forty -five minutes to nine hours. The 

 meteors appeared to radiate from Auriga, 

 or rather from a point between Taurus and 

 Auriga. Most of the meteors were small, 

 though two of them possessed extraordina- 

 ry brilliancy. In a small work on cometa 

 and meteors, published three years ago, 

 Mr. Kirkwood called attention to the fact 

 that meteoric showers had been observed 

 at the same period of the year in 1436, 

 1439, 1743, and 1798. Returns of the 

 shower were observed in 1838 and 1841. 

 He recommends that a careful watch be 

 kept in future about the same period say, 

 from the 16th to the 20th of October. 



