December, 1912.] 



471 



The object of the cotton investigation is to encouiage the production 

 of this crop in sufficient quantities to supply the local demand for raw 

 cotton and yarn, and for the local manufacture of cheap cotton goods. 

 The larger part of the importations of the first two classes and a large 

 part of the third come from China and other eastern countries. 



IS THE EARTH SHRINKING? 



The following letter appears in Nature of November 21st, 1912:— I have 

 carefully looked at this question from every point of view which presented 

 itself to me, and doubt very much whether any direct evidence will ever 

 be forthcoming on this subject, unless it should one day be established 

 that the changes of magnetic declination are associated with a slight 

 difference of rotation between the core of the earth and its crust, for 

 such a movement would have to be explained by a difference of rate of 

 contraction between the two. 



The foldings and crackings of the earth's surface have been attributed 

 to variations in the rate of cooling of the earth. Thus, whenever this 

 rate is accelerated, the surface cools faster than the core and should crack 

 like a drying ball of clay ; whenever the cooling rate is diminished, as 

 assumed by Lord Kelvin, the core should shrink faster than the skin, 

 like a drying apple, and folding should occur. But to my mind, as 

 recently explained in " Unity in Nature," such effects would be entirely 

 masked by such foldings and crackings as are slowly progressing even 

 today, for the sediment which is being constantly deposited on the 

 floors of the oceans must cause the underlying strata to grow warmer 

 and to expand in every direction, resulting in slight local risings, which 

 are most marked near the mouths of large rivers, and in distinct bulejings 

 and foldings of the weakest lines of the earth's crust, which are the 

 mountain ranges. On the other hand, the gradual wearing away of the 

 surfaces of the continents and mountain ranges, must cause the under- 

 lying strata to cool, to shrink and to crack. The suggestion would 

 certainly more than account for all the foldings, faidts and cracks to be 

 tound iu the earth's crust, even if a considerable allowance be made for 

 those cases in which the expansions and contractions occur in the same 

 direction, and partly balance each other. 



C. E. STROMEYER. 



"Lancefield," West Didbury, 

 November 7, 1912. 



PARA SEED SUPPLY. 



According to Tropical Life (1912, 8, 72), it is estimated that on certain 

 estates Hevea trees in full bearing will produce about 8 tons of nuts per 

 100 acres, or assuming 200 trees per acre, under 1 lb. per tree. The same 

 journal continues that on this estimate the 40,000,000 rubber trees stated 

 to exist in Malaya alone should yield 18,000 to 20,000 tons of seeds per 

 annum, whilst supplies from Ceylon and elsewhere should amount to a 

 further quantity of 40,000 tons and that planters will eventually find it 

 advantageous to utilise the seed, especially as the increased production of 

 rubber is likely to lower its market value. —Imperial Institute Bulletin. 



