TROPICAL NIGHTS. 



when a strong and pliant substance is I 

 wanted, the ^cc^nof composition, in which 

 the caoutchouc predominates, is to be pre- 

 ferred, 



A suhstance like leather may be formed 

 by joining togetlier several thicknesses 

 before they are dry. When leather for 

 the soles of shoes is required, JNJr. Han 

 cock jjroposes to use as the groundwork, 

 wool and cotton in equal quantities. For 

 pipes, straps, &c., he proposes chopped 

 hemp and cotton or flax; and when smooth 

 surfaces are wanted, the substance must be 

 pressed between polished metallic plates. 

 — Edinburgh Journ, of Science. 

 — -^ — 



From the Edinburgh New Philosophical Journal. 



CONNECTION BETWEEN METEOROLOGY 



AND VEGETATION. 



JNI. Bousingault has addressed a note to 

 the Jlcadernie des Sciences of Paris, which 

 is entitled Comparative examination of 

 the iMel ear oloiiical circumstances under 

 which our common grains, [the Cerealia) 

 Turkey-wheat, maize, and potatoes, ve- 

 getate at the Equator, and in tlie tem- 

 perate zone. — In this examination the 

 autb.or has first made investigations into 

 the lime which elapses between the first 

 springing of the plant and its full maturi- 

 ty. He then determined the temperature 

 of the space of time which separates these 

 two extreme epochs of vegetable life. By 

 comparing tliese data concerning any given 

 ])lant which is cultivated both in Europe 

 and America, he arrives at this curious re- 

 sult; that the number of days that sep- 

 arates the commencement of vegetation 

 from its maturity, is more considerable in 

 ])roportion as the mean temperature, under 

 the influence of which the plant grows, is 

 less; the duration of th.e vegetation will be 

 equal, however different the climate may 

 be, if tliis temperature is identical in the 

 two places; and it will be shorter or long- 

 er according as the mean heat of the pe- 

 riod of time necessary for the accomplish- 

 ment of the vegetatioQ, is itself greater or 

 less, in other words, the duration of the 

 vegetation appears to be in the inverse 

 ratio of the mean temperatures. So that 

 if you multiply the number of days dur- 

 ing which any given plant vegetates in 

 these distinct climates^ by the mean tem- 

 perature of the actual period of its vege- 

 tation, you will obtain numbers which are 



very nearly equal. This result is not only 

 remarble, inasmuch as it seems to indicate 

 that, under all climates the same annual 

 plant receives, in the course of its exist- 

 ence, an equal quantity of heat; but it 

 leads also to a practical result, in enabling 

 us to decide upon the possibility of intro- 

 tducing any particular vegetable into a 

 country as soon as we know the mean 

 temperature of the month there. — 



1 From the same. 



TROPICAL NIGHTS. 



By the by, I travelled by night to 

 avoid the mid-day vertical sun, and I now 

 from experience, advise my friends never 

 to follow my example. No evaporation 

 takes place, you perspire copiously, with 

 which, and the excessive dew, your clothes 

 get saturated, hanging on you like wet 

 leather, impeding every motion, and thus 

 increasing your fatigue. Your breathing 

 is less free, and you get an occasional puff 

 of cold damp air, which instead of refresh- 

 ing, only adds to your discomfort; in 

 short, you become completely oppressed. 

 But in the sun, what a change; evapora- 

 tion rapidly progresses, your dress acts like 

 a wine-cooler, you get rid of the oppressive 

 sense of heat, become stimulated, and 

 march on excessively relieved. One point 

 however must never be neglected, to keep 

 a considerable thickness of clothing upon 

 your head, you may then bid defiance to 

 mere heat. On the subject of tropical 

 nights, it occurs to me that there is a rather 

 singular affection to which the human 

 frame is subject, and several medical gen- 

 tlenien to whom I have spoken, seem to 

 me to entertain rather erroneous views as 

 to its origin. 1 allude to what is vulgarly 

 called inoon-struck. Dr. Wells, in his 

 admirable Essay on Dew, has shown that 

 a niutual interchange of radiated heat takes 

 j)lace, in ordinary circumstances, between 

 all bodies, and that on this depends the 

 preservation of temperature. On brilliant 

 moonlight and other cloudless nights, how- 

 ever, all exposed bodies do not receive a 

 quantity equal to that which they shed 

 forth. The want of clouds prevents them 

 receiving that vast quantity which would 

 otherwise be shot back fron the sky in 

 consequence; equality of temperature is 

 not maintained. All those bodies which 

 lie favourably, some more than others, be- 



