POPULAR MISCELLANY 



141 



rarer metals, the oxygen-furnace, and the 

 atmospheric gas-furnace, and, in its incipi- 

 ent stage, the electrical furnace. The suc- 

 cess of air-refrigerating machines and the 

 economic distillation of sea-water are de- 

 pendent on the same knowledge. Engineer- 

 ing and electrical science are brought into 

 close relations in the construction of tele- 

 graph and cable lines, in the development 

 and application of dynamo-machines and 

 dynamo-energy, and in electric lighting, 

 telephony, and microphony. In navigation, 

 the engineer avails himself of optical sci- 

 ence in the equipment of lighthouses ; of 

 pneumatics in Sir William Thomson's appa- 

 ratus for taking quick soundings, and of 

 magnetic science in his adjustment of im- 

 proved compasses. Mathematical principles 

 enter into the construction of ship-models. 

 In the processes of the preparation from 

 the ore of various metals, "it is essential 

 that the engineer and the chemist should 

 either be combined in one and the same 

 person, or go hand in hand." The chemist 

 and the microscopist have to be called in to 

 ascertain the purity of every contemplated 

 source of water-supply ; and the chemist, 

 when it is desired to convert a hard water 

 into soft. Engineers must consult the geolo- 

 gist before they can intelligently make esti- 

 mates of the works they are about to under- 

 take. In biology, the engineer learns from 

 the botanist the qualities of the various woods 

 he occasionally uses in his work, and has the 

 " germs " in view in arranging for the purity 

 of water-supply and for ventilation. Lastly, 

 great works of engineering facilitate geo- 

 graphical exploration, and are called into 

 existence by the dictates of the economist. 

 The speaker closed his address with a trib- 

 ute to the memory of Sir William Siemens. 



CnltivatioQ of Cacao. — The cacao - tree 

 flourishes in the hot i-egions of America, and 

 has been cultivated since the conquest in 

 Mexico, Guatemala, and Nicaragua. To se- 

 cure success, the cacao-plantation must be 

 made in new land, for the tree requires a 

 rich, deep,' and moist soil, and heat. The 

 best situation is cleared forest-land, so in- 

 clined as to permit its being iri'igated. The 

 cultivation of the trees often ceases to be 

 profitable when the temperature falls below 

 73°. The cacao seldom blossoms till it is 



thirty months old. The planters destroy the 

 first flowers, in order to prevent fruiting be- 

 fore the fourth year. There are few plants 

 in which the flower is so small and so dis- 

 proportioned to the size of the fruit. A bud 

 measured by M. Boussingault, at the time of 

 its expansion was not more than four milli- 

 metres broad. The flesh - colored corolla 

 was composed of ten petals surrounding five 

 silver-white stamens. The flowers did not 

 appear singly, but in bouquets on every part 

 of the trunk, on the principal branches, and 

 even on the salient wood-roots. The fruit 

 comes to maturity in about four months af- 

 ter the fall of the flowers. It is about ten 

 inches long and three or four inches in di. 

 ameter, slighty curved, weighs three hundred 

 or five hundred grammes, and is divided into 

 three lobes. Its color varies from a green- 

 ish-white to a red-violet. The pericarp is 

 furrowed longitudinally within ; the flesh or 

 pulp is rosy-white and acid, and generally en- 

 velops twenty fine, white, oily kernels which 

 in drying assume a superficial brown tint. 

 Two principal crops are harvested every 

 year, but on large plantations the gathering 

 is going on all the time, and it is not uncom- 

 mon to see trees bearing both flowers and 

 fruits at the same time. After breaking the 

 shell, the nuts are taken out and exposed to 

 the sun. In the evening they are piled up 

 under a shed. An active fermentation soon 

 sets in, which must not be allowed to go too 

 far, and, accordingly, the nuts are on the 

 next day spread out in the air. The cultiva- 

 tion of a cacao-plantation does not demand 

 much labor. One man can take care of a 

 thousand trees. The most serious difficul- 

 ties are the dangers from storms, which are 

 very destructive to the fruit ; otherwise the 

 principal duty of the attendant is to protect 

 the crop from animals. The cacao is shelled 

 by roasting at a moderate heat, in which 

 process it acquires, like the coffee-bean, an 

 odor arising from a minute proportion of a 

 volatile principle which it contains. This 

 is the peculiar aroma which we perceive in 

 chocolate. The cacao-beans are rich in nu- 

 tritious principles, containing a fat, nitro- 

 genous substance analogous to albumen and 

 caseine, theobromine and ternary compounds, 

 all of which vary somewhat in their relative 

 quantities. The theobromine is almost iden- 

 tical with the cafl'eine of coffee and the theine 



