February 



I, i; 



SCIENCE. 



85 



tible influence in preventin}^' the occurrence of tornadoes, or in 

 assuaging their violence. 



In this connection, it should not be forgotten that the conditions 

 which give rise to the development of tornadoes exist in the cloufi- 

 regions of the atmosphere, and not at the surface of the earth. 

 Forests would prevent the occurrence of whirlwinds, because these 

 phenomena depend upon the unstable state of the atmosphere at 

 the earth's surface, where the conditions are favorable for the sun's 

 heat to accumulate in the surface strata of the soil, and thus super- 

 heat the air resting upon it. A heavy growth of timber or rank 

 vegetation will prevent this action of the sun's rays. 



Whenever a tornado- cloud encounters a forest, the destruction 

 is complete and terrible. The forces of the tornado-cloud are 

 quickly brought into operation, and maintained continuously while 

 the phenomenon e.tists. They are not affected by having to meet 

 in rapid succession totally different objects, different in size, strength, 

 shape, materials, composition, structure, relative position, etc. 



The width of the path of destruction, as determined from the 

 records of 88 years, varies from 10 to 10,560 feet, the average being 

 1,369 feet. The length of the tornado-track varies from 300 yards 

 to about 200 miles, the average being 24.79 miles. The velocity of 

 progression of the tornado-cloud varies from 7 to 100 miles per 

 hour, the average being 44. 1 1 miles. These extremes may often 

 occur in different portions of the track of a single tornado. The 

 shortest time occupied by the tornado-cloud in passing a given 

 point varies from " an instant " to about 20 minutes, the average 

 being about 74 seconds. 



The month of greatest frequency, that is, the month embracing 

 the largest number of days in which tornadoes occurred, is May. 

 The prevailing direction of the progressive movement of the tornado- 

 cloud is north-east. The vortex wind velocities of the tornado- 

 clcwd vary from 100 to 500 miles per hour, as deduced from actual 

 measurements. Velocities of from 800 to 1,000 miles per hour are 

 extremes that have been reported, but may not be altogether reli- 

 able. Theoretical velocities of 2,000 miles and over per hour, based 

 upon certain assumed atmospheric conditions, have been deduced. 

 Such velocities are mathematically possible, but not meteorologically 

 probable. 



The concomitants of the tornado are, an oppressive condition of the 

 air ; the gradual setting-in and prolonged opposition of northerly 

 currents and southerly currents over a considerable area ; a high tem- 

 perature, and the presence of considerable moisture ; a gradual but 

 continual fall of the thermometer with the prevalence of northerly 

 currents, and a rise with the predominance of southerly ; a rapid 

 decrease of temperature with increase of altitude ; a decided gradi- 

 •ent of temperature across the line of progressive movement ; huge 

 masses of dark and portentous clouds in the north-west and south- 

 west, possessing a remarkable intensity of color, usually a deep green ; 

 a remarkable rolling and tumbling of the clouds, scuds darting from 

 all points of the compass towards a common centre ; hail and rain 

 accompanying the tornado, the former either in unusual size, form, 

 or quantity, and the latter either remarkable in quantity or size of 

 drops ; the presence of ozone in the wake of the tornado ; a re- 

 markable roaring noise, like the passage of many railroad-trams 

 through a tunnel. 



The cloud generated by the vortex assumes the form of a funnel, 

 with the smallest end towards the earth. This explains the re- 

 markable contraction of the storm's path. Upon reaching the 

 earth's surface, the vortex has four motions: viz., first, the whirl- 

 ing or gyratory motion, always from right to left ; second, the pro- 

 gressive motion, generally from some point in the south-west 

 quadrant to some point in the north-east quadrant ; third, the 

 curvilinear motion ; fourth, oscillatory motion. 



The characteristic effects of a tornado are, objects are drawn 

 towards the vortex from every point of the compass ; objects pass- 

 ing into the vortex are thrown upwards and outwards by the vorti- 

 eal action of the engaged air ; structures are literally torn to pieces 

 by the vortical action of the air, evidence of which is afforded by 

 the fineness of the debris, and also its disposition in the storm's 

 path ; the debris is thrown inward from each side of the storm's 

 path ; light objects are carried to great heights and also to great 

 •distances ; objects are carried inward and upward by the centrip- 

 etal, and outward by the centrifugal, forces of the vortex ; weight 



and size are conditions which generally present immaterial values 

 to the power of the tornado ; persons are stripped of clothing ; 

 fowls and birds are denuded of feathers and killed ; trees are 

 whipped , to bare poles ; heavy objects are carried for miles in the 

 air ; long and heavy timbers are driven to considerable depths in 

 the solid earth ; the vortex is completely filled with flying debris; 

 timbers are driven through the sides of buildings ; sand and gravel 

 are driven into wood ; the strongest trees are uprooted, or twisted 

 off near the roots ; men and animals are terribly mangled by con- 

 tact with flying debris and by being rolled over the ground for a 

 considerable distance ; in the path of the storm all vegetation is 

 destroyed ; railroad-trains are thrown from the track; iron bridges 

 are completely dismantled and carried from their foundations ; heavy 

 bowlders, weighing tons, are rolled along the earth ; the largest 

 railroad-engines are lifted from the tracks on which they rest ; all 

 objects, whether metal or non-metallic, magnetic or non-magnetic, 

 simple or compound, animate or inanimate, are acted upon in a 

 similar manner. 



THE SITUATION IN SAMOA. 



The continuous disturbances on the Samoa Islands, and their 

 bearing upon questions of great political importance, give to these 

 islands a special interest. The group consists of thirteen islands, 

 only three of which are of commercial interest, — Savaii. Upolu, and 

 Tutuila. Savaii is the largest island of the three, measuring some 

 40 miles from east to west by 20 miles from north to south, and 

 having an area of 700 square miles. It has no harbor of any impor- 

 tance, and in this respect it contrasts strongly with Upolu and 

 Tutuila. The little bay of Mataatu, in the extreme north of the 

 island, is the only place where large vessels can anchor ; but even 

 it is not safe from November to February. The interior of the 

 island is occupied by tvvo mountain-ranges of volcanic origin. It 

 has no rivers or streams, the water filtering away through the po- 

 rous soil. Where the mountains approach the coast, the latter is 

 very steep and inaccessible, while in other places a well-wooded 

 strip of alluvial land is found, on which numerous villages are situ- 

 ated. The sterility of the interior of this island has always been a 

 barrier to all settlement or cultivation, and even to the visits of 

 travellers and explorers. 



Upolu, which covers an area of 550 square miles, is also moun- 

 tainous, but it is well wooded and fertile, and possesses several 

 considerable streams, although they are, of course, not navigable. 

 On the northern coast of this island lies Apia, the chief town of 

 the whole Samoan group. It is prettily situated, having a back- 

 ground of mountains thickly wooded, and a foreground of harbor 

 and coral reefs. The harbor consists of two portions, the most 

 westerly being the best for vessels that intend to remain for any 

 length of time, especially during the rainy season. For sailing- 

 craft, a steady breeze is absolutely necessary on entering or leav- 

 ing the harbor, as a strong current sets along its entrance. 



Passing down the coast east of Apia, a .succession of beautiful 

 bays are met with. At the distance of from half a mile to two 

 miles from the shore a coral reef protects this portion of the island 

 for nearly twenty miles. At high tide canoes and boats can pass 

 between this and the mainland, and thus a great deal of the insular 

 traffic is carried on. 



As seen from the sea, there are not many islands in the Pacific 

 that present a more beautiful or picturesque appearance than 

 Upolu. It shows a bold and majestic front, the central range 

 being not less than 3,000 feet high, and wooded almost to its sum- 

 mit. It is throughout a very fertile island, and fully equal to the 

 best portions of the Fiji group. 



Tutuila is about 17 miles long and 5 broad. On its southern 

 side is the deep bay of Pagopago, which almost cuts the island in 

 two. This harbor, which is one of the best in the whole South 

 Pacific, is surrounded by hills from 2,000 to 3,000 feet high. Sur- 

 rounding the harbor at their base is a small strip of level land. 

 The harbor is half a mile wide at its entrance, and runs north and 

 south for a distance of a mile, when it turns in a westerly direction, 

 and opens out into a fine sheet of water. It is somewhat difficult 

 for sailing-vessels to leave, in consequence of the trade-winds 

 blowing directly into it ; but for steamboats it is unsurpassed by 



