138 



THE POPULAR SCIENCE MONTHLY. 



size, and a palatable, fleshy, smooth-skinned 

 covering like a plum. The nut affords an 

 oil, which solidifies under a slight decrease 

 of temperature, and is used throughout 

 North Africa as a substitute for butter. 

 The Farkia higlobosa {runno-kan) of the 

 same region, a leguminous plant, furnishes 

 an excellent food in its seeds, which are 

 eatable while still unripe. The ripe seeds 

 contain a thick, saffron-colored marrow in- 

 closing black, shining grains. The meal 

 made from them forms when mixed with 

 water or milk a pap, which has a sweet and 

 pleasant taste at first, but soon cloys. Re- 

 lieved with sour milk or tamarind-juice, it 

 forms a dish healthful and enjoyable to all. 

 The wool-tree {Eriodendron anfractiiosum) 

 is the third characteristic tree of the coun- 

 try. It rises straight up, with thick, hori- 

 zontal branches arranged in whorls one 

 above the other, and derives its name from 

 its fruit, which bursts like the pods of cot- 

 ton and discloses a similar mass of fibers, 

 lustrous and soft as eider-down. This 

 " wool " is used for the stufiing of cushions 

 and mattresses and for the wadding-armor 

 of the heavy cavalry. It has the valuable 

 property of never becoming so compact but 

 that it can be restored to its original volume 

 by a short exposure to the sun. The tree is 

 a favorite place of refuge for the negroes in 

 time of danger. Taking their children and 

 goods up with them, they secure an excel- 

 lent natural fortress among the whorls of 

 its limbs. 



Disposition of Sewage. — Professor Hen- 

 ry Robinson remarks, in a paper on " Home 

 Sanitation and Sewage Disposal," that the 

 latter question should be regarded as involv- 

 ing a combination of sanitary and agricul- 

 tural interests, of which the first is para- 

 mount and the latter should be disregarded 

 when incompatible with it. Sewage is puri- 

 fied in passing through the soil by one or 

 more of three processes : 1. By simple fil- 

 tration or removal of the suspended matter ; 

 2. By the precipitation and retention, in the 

 soil, of ammonia and various organic sub- 

 stances previously in solution ; and, 3. The 

 oxidation of ammonia and of organic mat- 

 ter with the aid of living organisms. A fil- 

 ter-bed may be constructed so as to have a 

 greater oxidizing power than would be pos- 



sessed by ordinary soil and subsoil, by lay- 

 ing over a system of drain-pipes a few feet 

 of soil obtained from the surface of a good 

 field, care being taken to select a soil con- 

 taining a considerable amount of carbonate 

 of lime and organic matter. Such a filter- 

 bed would be far more porous than a natu- 

 ral soil and subsoil, and would possess ac- 

 tive oxidiizng functions throughout its whole 

 depth. The presence of antiseptics inter, 

 feres with the fermentation, and refuse from 

 chemical works hinders the progress of pu- 

 rification. Much valuable information has 

 been published by Drs. Lawes and Gilbert 

 on the chemical changes that take place in 

 the soil under varying circumstances ; and 

 Dr. Angus Smith, a rivers pollution inspect- 

 or, has much to say in his last annua 1 re- 

 port on the action of air on sewage and the 

 mode of treating sewage so as to hasten 

 aeration ; while in a previous report he has 

 discussed the treatment of sewage by chem- 

 icals. Much information on these subjects 

 may also be found in Mrs. Robinson's work on 

 " Sewage Disposal " (Spon, London). Well- 

 adapted lands have been found capable of 

 purifying the sewage of about five hundred 

 people per acre. The average amount dis- 

 posed of in nineteen towns where broad ir- 

 rigation was practiced was equivalent to the 

 sewage of one hundred and thirty-seven peo- 

 ple per acre. 



Commnnieability of Disease by Food. — 



Except the diseases associated with tape- 

 worm and trichinae, the only animal diseases 

 which there is or has been ground for regard- 

 ing as transmissible to man, through ingest- 

 ed meat, are cattle-plague, swine-typhoid, 

 epizootic plcuro-pneumonia, foot-and-mouth 

 disease, anthrax and anthracoid diseases, 

 erysipelas, and tuberculosis. Mr. Francis 

 Vacher, medical officer, of Birkenhead, Eng- 

 land, having examined the evidence in re- 

 spect to the communicability of these seven 

 diseases, has announced the conclusion, in 

 the " Sanitary Record," that only two of 

 them — foot-and-mouth disease and anthrax 

 — can as yet be pronounced communicable 

 to man by infected flesh, while the commu- 

 nicability of the others, although it can not 

 be positively denied, remains unproved. 

 Cattle-plague has been supposed to be al- 

 lied to various forms of human disease, but 



