September 24, 1886.] 



SCIENCE. 



275 



those facing west are nearly as seriously injured ; 

 those facing south follow, but are much less in- 

 jured than the two former ; and those facing north 

 are least injured, but only slightly less than the 

 southerly walls. 4. When corners of buildings 

 are tkrown out, they have gone most frequently 

 to the north-east, next to the south-west, third to 

 the north-west, and least frequently to the south- 

 east. So many isolated observations are incon- 

 sistent with these generalizations, however, that 

 little value can be attached to them. Similar in- 

 consistencies are observed in the behavior of the 

 marble and granite shafts in marble-yards and 

 cemeteries. Of those which have been overturned, 

 the larger number have been thrown either to the 

 north or south, but some have gone in various 

 other directions ; many have suffered torsional 

 displacement, but of these some have turned with 

 others against the sun ; while others are dis- 

 placed laterally without overthrow, and in as 

 many directions as there are compass-points. 

 Chimneys, too, have been twisted both with and 

 against the sun, and during their oscillations 

 have ' walked ' in various directions. A Charles- 

 ton chimney twisted with the sun, and slightly 

 displaced southward, is shown in fig. 3 : and 

 a neighboring monumental shaft turned in the 

 opposite direction, and displaced north-eastward, 

 is represented in fig. 4. Perhaps the discre- 

 pancies among these observations may eventually 

 be eliminated, and the apparent confusion reduced 

 to order ; but for the laresent, in f erences as to the 

 azimuth of the wave-paths in Charleston and im- 

 mediate vicinity are premature. 



It is remarkable that the intensity of the seismic 

 action has varied greatly within the limits of the 

 city of Charleston. Thus in certain quarters the 

 buildings have escaped with trifling injury, while 

 similar and similarly oriented buildings in other 

 quarters have been completely destroyed ; and aU 

 possible intermediate phases of injury are found 

 in different parts of the city. The numerous ob- 

 servations on the variable intensity of the dis- 

 turbance in Charleston and elsewhere in South 

 Carolina have not yet been collated and digested ; 

 but it would appear that there are large areas 

 within which the intensity of the disturbance cul- 

 minated (and Charleston is one of these), and, 

 moreover, that within these areas themselves there 

 are foci or nodes of maximum vibration circum- 

 scribed and separated by annuli in which the dis- 

 turbance was less severe. 



A few fissures, such as those abounding at Sum- 

 merville, occur in Charleston and vicinity, and 

 some small craterlets have also been observed in 

 the neighborhood. 



A number of slight tremors were experienced in 



Charleston. They differed from those felt at 

 SummervUle, 1°, in less intensity and greater 

 duration ; 2°, in direction, which was manifestly 

 more nearly lateral than vertical, though the 

 azimuth was not accurately determined ; and, 3°, 

 in the absence of detonations or other sounds than 

 such as might be attributed to movements in 

 furniture, in neighboring buildings, etc. 



Briefly, it appears, that within a radius of a 

 dozen miles somewhere near the centre of the dis- 

 trict affected, and within an area of remarkably 

 uniform topographic configuration and geologic 

 structure, the effects of the recent earthquake are 

 quite diverse : viz., that at Summerville the prin- 

 cipal effects are crushing of structures in the ver- 

 tical direction, and the formation of fissures with 

 the outflow of a considerable volume of water ; 

 that at Ten-Mile Hill, half-way between that 

 point and Charleston, the principal effects are 

 local deformation of the surface and the extravasa- 

 tion of a great volume of sand-laden water, with 

 combined crushing and lateral displacement of 

 structures ; and that in Charleston the predomi- 

 nant effects are lateral displacement in various 

 directions (without vertical crushing) and over- 

 throw of structures, torsional displacement and 

 overturning in different directions of monuments, 

 together with some Assuring of the surface and 

 the extravasation of small quantities of water. 



W. J. McGee. 



COMPRESSED AIR ON CABLE-ROADS. 



One of the minor annoyances in connection with 

 the cable street-railway system is the fact, that, 

 until the car is gripped to the moving cable, it 

 must depend for its motive power upon some other 

 agent ; that is, it must be run to and from the 

 car-house by hand or horse power ; and switching 

 from one track to another at the termini of the 

 road is usually accomplished in the same manner. 

 To dispense with this extra motive power, by 

 making each car temporarily self-propelling, is the 

 object sought in a series of experiments now in 

 progress on the Tenth Avenue cable-road in this 

 city. The experimental car is fitted w-ith a small 

 air-compressor, an air-engine, and several cylin- 

 drical air-tanks, placed beneath the body of the 

 car. The compressor is connected by a clutch 

 with one of the car axles ; and the engine or motor 

 is connected in a similar manner, though with the 

 addition of an intervening ti-ain of speed-reducing 

 gear-wheels. On a recent trial trip, the air-tanks 

 were filled to a pressure of about five atmospheres, 

 at the car-house, by means of a compressor. The 

 driver, or grip-man, then opened the valve admit- 

 ting air to the engine, and the car propelled itself 



