576 KANSAS CITY REVIEW OF SCIENCE. 



Again, two such wires as above, insecurely attached near each other, may 

 be brought into momentary contact and then separated, in which case an electric 

 arc, with its intense light and heat, will be established between them. In like 

 manner a conducting wire itself may be insecurely connected at some point, and 

 if the abutting ends are separated slightly during use, a similar arc with its in- 

 tense heat may be there developed. 



Turning to the dangers which might be expected from the electric lamp, it 

 is to be remarked, in -the first place, that these in the case of the arc lights de- 

 pend much upon the number of lamps operated on the same circuit. Thus, if 

 thirty or forty lamps are operated in series, the electro-motive force of the current 

 must be sufficient to maintain a corresponding number of arcs ; and therefore if 

 by any means many of these arcs are closed out, the electro-motive force of the 

 current available for the remaining ones Avould be so excessive that their arcs 

 might become excessively long, and even the metallic carbon holders and other 

 parts of the lamps constitute poles between which the arc would spring, melting 

 the metal-work and establishing a very dangerous system of combustion. 



To avoid this class of dangers, two provisions should be made. In the first 

 place some arrangement in the lamp itself by which, whenever the arc exceeds 

 certain safe limits, the current will be automatically diverted from it and carried 

 through a good and sufficient conductor ; and, in the second place, some appa- 

 ratus in connection with the electric generating machine by which the electro- 

 motive force of its current should be varied automatically in correspondence with 

 the resistance of the circuit, so that any diminution of such resistance, as by the 

 closing out of several arcs, should cause a corresponding diminution in the force 

 of the current generated. Numerous contrivances for both of these purposes 

 have been already carried to greater or less perfection and efficiency, and it is 

 manifestly possible by such means to secure immunity from risks of this sort. — 

 Sanitary Engineer. 



EARTHQUAKES OF 1881. 



Among the remarkable things for which 1881 will be long remembered are 

 its earthquakes. Not since the memorable years 181 1 and 181 2 has there been 

 such a wide circle of terrestrial disturbance as now exists. Seventy years ago 

 nearly the whole western hemisphere trembled under the strain of internal com- 

 motion. But the area in which the earthquakes were felt was bounded by the 

 two great oceans, and neither Europe or Asia suffered to any extent. The pres- 

 ent area of commotion seems to have no limits. Reports of violent earthquakes 

 have for many months past come from every quarter of the globe. The shocks 

 that desolated Chios in April rank as agents of destruction with the earthquakes 

 which destroyed Lisbon in 1755, Riobamba in 1797, and Caraccas in 1812. 

 The recurrence of earthquakes within a few days at Chios which have again 

 caused the inhabitants to flee for their lives, the shocks experienced at Agrani 



