58 



SCIENCE. 



[Vol. XVI. No. 391 



metal, as shown in Fig. 3, which is a perspective view of a motor, 

 with sliding base and starting-box complete. 



These machines are calculated to be equally efficient as dyna- 

 mos, and are coming into use in many small isolated incandescent- 

 light plants. For this purpose they are compound wound ; and 

 the regulation, it is claimed, is so perfect, that all but one lamp 

 may be suddenly turned off without moving rheostat or brushes, 

 and without noticeable change in the brilliancy of the remaining 

 lamp. 



THE LOUISVILLE TORNADO. 



Once in a great while the whole world is startled by such 

 an api3alling catastrophe as the Chicago Are of 1871 or the 

 Boston conflagration of 1873. Such disasters are entirely 



Grinnell, then we need not expect such a one again in about 

 the same number, excepting as an increase in the size and 

 frequency of towns in the tornado regions gives a more fre- 

 quent opportunity for such accidents. This may also be 

 said as true regarding the most serious fires. 



Just preceding this tornado the atmospheric disturbance 

 to the west and north-west of its development was unusually 

 marked; so much so, that all the region in which the violent 

 storms occurred were warned of their probable occurrence 

 nearly twelve hours in advance by the Signal Office at 

 Washington. The centre of the general storm at 7 a.m. 

 (Central time), or twelve hours before the tornado, was in 

 eastern Kansas, at which point the air-pressure was below 29.1 



-THE PEEEET MULTIPOLAR ELBCTEIC MOTOE. 



outside of the usual experience, and thus make a most pro- 

 found impression. Of such a character are to be regarded 

 the Grinnell (Iowa) tornado of April 17, 1882, and the more 

 recent one at Louisville on March 27, 1890, in which 76 peo- 

 ple were killed and $2,250,000 of property were destroyed. 

 It might be thought that every tornado has exactly the same 

 power, but does not show it because it does not happen to 

 strike where it can do the most damage. To a certain ex- 

 tent we might argue in precisely the same way about a fire. 

 Every fire, under such environments as mentioned above, 

 would reproduce the terrible effects, but we find that the 

 ordinary result of a fire is far different; and this is exactly 

 the truth in regard to tornadoes. No two tornadoes are alike 

 in their diameter or force. We may argue, however, that if 

 two thousand tornadoes have produced one such as that at 



inches. At 7 p.m. this storm had moved rapidly to central 

 Illinois, and just fifty-seven minutes later Louisville was 

 struck and partly destroyed. This fact, that we have a chart 

 of the meteorological conditions within an hour of this out- 

 burst, is very important. We find that the winds through- 

 out the tornado region were from the south and south-east; 

 and this current existed even up to the clouds, as we have 

 determined in so many cases before. In fact, the whole 

 circulation of the atmosphere was no whit different from 

 that noted again and again in such general storms. The 

 tornadoes were suddenly thrown into this atmospheric cir- 

 culation almost without warning. The velocity of the gen- 

 eral storm, moving nearly due east, was 38 miles per hour 

 from 7 to 11 a.m. of March 27, 39 miles per hour in the next 

 four hours, and 37 miles per hour in the four hours just 



