196 



SCIENTIFIC NEWS. 



[Mar. 2, 18 



From the fact that the flow is so immense, and that 

 the pressure is so well maintained, it is generally sup- 

 posed that a constant generation of gas must be going on 

 beneath the earth's crust. Occasionally reports get afloat 

 that such and such a well is giving out, but a good 

 authority states that in every instance it has been found 

 that the decreased pressure has been caused by some 

 obstruction in the piping, and that when this was 

 removed the original pressure was restored. 



The natural gas escapes from the earth at a very high 

 pressure, seldom under 100 pounds on the square inch, 

 and often much more. If, then, we remember that the 

 pressure of the gas we are accustomed to use in our 

 houses has a pressure of only about one-twelfth part 

 of a pound to the inch, some idea may be formed of 

 the almost unmanageable pressure in Nature's gas works. 

 This high pressure is a distinct advantage for the purpose 

 of conveying the gas long distances, as much smaller 

 pipes can be used, but the practical difficulties attending 

 the use of gas at a pressure of only a few pounds to the 

 inch are very considerable. The high-pressure gas is 

 usually passed into gas-holders weighted to a convenient 

 pressure for town distribution, but even this device is 

 not entirely free from risk. In Millerstown, Pa., on the 

 28th December last, the inhabitants were startled to 

 find that the gas flames in their houses shot up a foot 

 or so in height, and almost immediately afterwards they 

 were dismayed at seeing the flames reach the ceilings. 

 Fortunately prompt action was taken, or the town would 

 have been destroyed. The cause of the mishap was that 

 the ball of a regulating valve at the holder either fell off 

 or was removed, so that the full natural gas pressure 

 was thrown on the mains and service pipes. 



Our illustration, taken from Scientific American, repre- 

 sents a group of gas wells at Fort Scott, in Kansas, as 

 seen at night. These wells form one of the great natural 

 resources of the district, and at present there is more 

 gas than can be used, although pipes are laid throughout 

 the town for supplying light and fuel to everybody at a 

 mere nominal cost. An increasing number of manufac- 

 turing industries is being established at Fort Scott, but 

 in the meantime the scene at night time near the wells 

 is described as very striking. The flames from the wells 

 then look like gigantic torches, being twenty feet or 

 more in height. The whole of the surrounding country 

 is, in fact, illuminated by Nature's abundant provision. 



STORMS.— I. 



/^REAT as has been the progress in the science of 

 ^^ meteorology during the last twenty years, the 

 precise theory of the mechanism of storms and the 

 nature of cyclone currents has yet to be discovered ; or, 

 at all events, the somewhat contradictory hypotheses 

 which have as yet been put forward must be harmonised 

 and proved. Fortunately for the sailor, the "law of 

 storms " has been expressed in so simple a manner that 

 for the last half-century mariners have not only had a 

 set of simple rules for instant action in a hurricane, but 

 they have derived infinite advantage from them, and in- 

 numerable lives have been saved by the knowledge 

 which enables them to avoid an approaching storm. 



Before describing the nature of a cyclonic storm, it 

 may be well to give a brief account of the causes which 

 produce winds. Wind is the rush of air from a locality 



of high to one of low pressure. The reason for 

 the difference of pressure is often very difficult to deter- 

 mine, and of two meteorological events it is frequently 

 impossible to say which is cause and which is effect. 

 The " trade-winds " are easily accounted for by the 

 following facts. The air over the equatorial regions of 

 the earth, becoming heated by the greater power of the 

 sun, becomes rarified, and rises, causing a diminution ot 

 pressure. The air from the cooler regions of the north 

 and south flows in to take its place, and the air which 

 has risen moves towards the poles and becomes cooled,, 

 both by the actual decrease of temperature in the upper 

 regions of the atmosphere and by the heat lost by the 

 work done in its own expansion under the lower 

 pressure. It eventually descends, and thus completes 

 the circuit. The motion in the higher regions is there- 

 fore towards the poles, and the lower currents blow 

 towards the equator. 



Now, the surface of the earth at the equator moves at 

 the rate of 24,800 miles per day, or seventeen miles per 

 minute, and at the latitude of Constantinople or New 

 York the velocity is about three-quarters, and at 

 Christiania, on latitude 60, it is one-half as great. 

 When a mass of air moves towards the equator the earth 

 will outrun it, on account of the greater speed at which 

 the surface is travelling. Instead of blowing north and 

 south, the wind will be north-east and south-east. These 

 regular winds are only found near the equator, but it 

 must not be supposed that there are two belts, one on 

 each side of the equator, in which these breezes blow 

 steadily all the year round, as suggested by the maps in 

 the " physical " atlases. They are considerably disturbed 

 by the constantly changing winds in the tropics. 



Every wind is part of a current circulating in a more 

 or less closed course. It is evident that a wind must go 

 somewhere, and that air must come from somewhere 

 else to fill up the space which it has left. If the density 

 of the air were uniform, and lay on the surface of the 

 earth like an ocean, the depth would be a little less than 

 five miles. But Mr. Glaisher has ascended in a balloon 

 to a height of about seven miles, and the air, which was 

 about one-third of the density of that on the surface of 

 the earth, could be breathed, and sustained the balloon. 

 The motions of a uniform ocean of air above us would be 

 much less difficult to deal with, though it must not be 

 imagined that they would be the same as those of water, 

 for the great elasticity of the air introduces a number of 

 other considerations, and the variation of its density at 

 different heights complicates the matter still further. 



Most people have noticed that it is very difficult to 

 empty a basin having a plug at the bottom without setting, 

 up a whirlpool. The same is to be seen in emptj'ing a 

 funnel. The reason is similar to that which has been 

 given to account for the westerly direction of the trade- 

 winds. Any small portion of the water which happens 

 to have a circular motion (and any motion in the basin 

 which is not radial must be to some extent circular) will 

 have its angular velocity increased when it is drawn 

 towards the centre, as it has a smaller circle to travel in. 



When a mass of air rises by becoming warmed, there 

 will be an inrush from all sides near the surface of the 

 earth to take its place, and there will almost invariably 

 be a tendency to circular motion, slow at the outside and 

 more rapid as it approaches the centre, where the stream 

 turns upward. From causes which are not very clearly 

 understood, the direction in the northern hemisphere is 

 almost always contrary to that of the hands of a watch^ 



