January 1, 1896.] 



KNOWLEDGE 



9 



of the time. The relation is due to the fact that the force 

 of gravity is contimtally acting. The relation may be 

 otherwise stated by saying that the time ig proportional to 

 the square root of the length. Now, in our U tube the 

 portion E F, at the moment represented, is the crest of ?>■ 

 wave, and G H is the succeeding trough." The interval of 

 time which will elapse before G H is the crest is propor- 

 tional to the square root of the length of the column of 

 water ; or, the velocity with which a wave-crest appears to 

 travel over the surface of the water is greater in proportion 

 to the square root of the wave-length. From this we see 

 that, if any cause of disturbance starts a wave of a certain 

 velocity, the distance from crest to crest will depend upon 

 this velocity, and in the precise manner above stated. 

 From the Imown length of the seconds-pendulum (or, to 

 put it otherwise, fi'om the known value of the acceleration 

 due to gravity) the wave-length proper to any given 

 velocity can be calculated. The following approximate 

 rule will be found useful for numerical calculations relating 

 to water waves, nz., that — five times the wave-length is 

 numerically equal to the square of the velocity, lengths 

 being expressed in feet and time in seconds. This rule 

 gives a velocity of about forty feet per second, or twenty- 

 seven miles per hour, for waves three hundred feet from 

 crest to crest, such as are observed in the Atlantic after a 

 storm. 



The depths of the ocean are undisturbed by the waves 

 with which the wind covers the surface, for the excursions 

 of the swinging particles diminish very rapidly as the dis- 

 tance from the surface increases. In an Atlantic storm- 

 wave, with surface particles swinging round a circle of forty- 

 foot diameter, the motion at a depth of three hundred feet 

 is calculated to be not more than half an inch ; so that we 

 may say that at a depth greater than the distance from 

 crest to crest the water is undisturbed by winds, and, con- 

 versely, where there is such a clear depth of water the for- 

 mation and the motion of the largest wind-waves is not 

 hindered or modified by the sea bottom. Some seas, how- 

 ever, are really very shallow. The depth of the North Sea 

 is not more than half the distance from crest to crest of a 

 full-grown Atlantic wave ; it would be difficult to find a 

 spot in the North Sea where St. Paul's Cathedral would 

 be completely submerged. 



When the depth of water is small relatively to the wave- 

 length the motion of the water particles is greatly modified, 

 and we encounter the more varied phenomena of waves in 

 shallowing water, culminatmg in the waves of the sea- 

 shore and the ever-beautiful breaking wave — of all of which 

 more anon. 



THE BANANA. 



By ElCHARD Beynon'. 



NEVER in the history of the world's trade has there 

 been so marked an example of an edible article 

 of commerce attaining within a comparatively 

 short period the popularity achieved by the 

 banana. It is not long ago that this luscious 

 product of the tropics was only heard of as a vegetable 

 curiosity. Occasional parcels were brought to England 

 by vessels trading from the West Indies or the West 

 African islands ; but these reached no farther than the 

 narrow circles of the friends to whom they were sent. The 

 omnivorous British public remained practically ignorant of 

 the rich, wholesome fruit which nature was ready to produce 



• It is to be borne in mind that in the proportions obtaining in 

 actual waves, the vertical limb of the supposed tube is short compared 

 with the length of the horizontal part. 



SO bountifully. Now, however, no fruiterer's stock is 

 complete without its bunches of richly-tinted bananas ; 

 while the enterprise of the "coster " and other itinerant 

 vendors has placed the fruit within the reach of the 

 poorest. 



Originally the banana was a native of the eastern tropics, 

 but now it is cultivated in all tropical and sub-tropical 

 countries, whether in the Old or New World. 



The plant itself is a peculiar one, the stem, which attains 

 a height of fifteen or twenty feet, being practically formed 

 by the sheathings of the leaves, the blades of which reach 

 the very respectable dimensions of eight or ten feet in 

 length and eighteen inches or two feet across. The fruit 

 clusters, which branch from the stem, have been known to 

 weigh upwards of ninety and even a hundred pounds. A 

 bunch of average bananas contains eight hands of ten 

 bananas, while those of inferior quality will consist of but 

 six or seven hands. 



The productiveness of the banana plant is enormous. 

 We are sometimes wont to refer to the productive power 

 of grain or the potato as examples of extraordinary fertility. 

 But, according to Humboldt, the banana is more than a 

 hundred times as productive as wheat and forty-four times 

 as productive as the prolific potato. 



As a complete article of food, containing in itself the 

 principal elements necessary to preserve the human 

 machine in health and strength, this fruit is one of the 

 completest with which nature has furnished us. The 

 principal constituent is of course water, which practically 

 forms three-fourths of the weight of the banana. Sugar, 

 pectine, etc., compose about twenty per cent., while 

 nitrogenous matter is, roughly speaking, accountable for 

 the remaining five per cent. 



In many tropical areas the banana is the staple food, 

 and from the unripe, sim-dried fruit a most nutritious flour 

 is manufactured. In fact, this fruit is to a great section 

 of the inhabitants of the tropics, and the regions adjoining, 

 what wheat is to the European and rice to the Hindoo. 



Twenty-five years ago, some men interested in the 

 New York fruit trade prophesied a big future for this fruit. 

 Thinking that there might be " money in the business," a 

 fruit merchant introduced to the buyers of New York a 

 shipment of four thousand bimches ; but this initiatory 

 effort does not seem to have met with much success. Ten 

 years later, another consignment of ten thousand bunches 

 was shipped from .Jamaica, andno dilficulty was experienced 

 in securing a ready sale. Xi'ir, the trade in bananas 

 between New York and the West Indies forms a special 

 department of commerce, for which vessels are specially 

 built and equipped. 



The quantity of bananas shipped from West Indian and 

 adjacent ports into the United States now amounts to 

 thirteen or fourteen million bunches annually, valued at 

 considerably over four millions sterling. Our own posses- 

 sion of Honduras exported, in 1880, bananas to the value 

 of seven hundred pounds, while at present the annual value 

 of this fruit exported is close upon fifty thousand pounds. 

 From one port alone, on the shores of the Caribbean Sea, 

 two hundred and fifty thousand pounds worth of bananas 

 are exported each year. 



The fruit which finds its way to England comes almost 

 entirely from ^ladeira and the Canary Islands. Before 

 long, however, the West Indian banana will enter the field 

 as a powerful competitor, the arrangements for the safe 

 and speedy sea-carriage of the fruit now rendering auch a 

 contingency quite feasible. 



The bananas intended for export are cut when green, 

 and consequently unripe, and carefully packed in long 

 and loosely constructed baskets, or wooden crates. The 



