EXAMPLES OF THE EXPLANATION OE LAWS. 



315 



borthem regions, where the polar 

 direction is nearly perpendicular to 

 the horizon, all horizontal motions of 

 conductors will produce electricity ; 

 horizontal wheels, for example, made 

 of metal ; likewise all running streams 

 will evolve a current of electricity, 

 which will circulate round them ; and 

 the air thus charged with electricity 

 may be one of the causes of the 

 aurora borealis. In the equatorial 

 regions, on the contrary, upright 

 wheels placed parallel to the equator 

 will originate a voltaic circuit, and 

 waterfalls will naturally become elec- 

 tric. 



For a second example ; it has been 

 proved, chiefly by the researches of 

 Professor Graham, that gases have a 

 strong tendency to permeate animal 

 membranes, and diffuse themselves 

 through the spaces which such mem- 

 branes enclose, notwithstanding the 

 presence of other gases in those spaces. 

 Proceeding from this general law, and 

 reviewing a variety of cases in which 

 gases lie contiguous to membranes, 

 we are enabled to demonstrate or to 

 explain the following more special 

 laws : I St. The human or animal 

 body, when surrounded with any gas 

 not already contained within the 

 body, absorbs it rapidly ; such, for 

 instance, as the gases of putrefying 

 matters : which helps to explain 

 malaria. 2d. The carbonic acid gas 

 of effervescing drinks, evolved in the 

 stomach, permeates its membranes, 

 and rapidly spreads through the sys- 

 tem. 3d. Alcohol taken into the 

 stomach passes into vapour and 

 spreads through the system with great 

 rapidity, (which, combined with the 

 high combustibility of alcohol, or, in 

 other words, its ready combination 

 with oxygen, may perhaps help to ex- 

 plain the bodily warmth immediately 

 consequent on drinking spirituous 

 liquors). 4th. In any state of the 

 body in which peculiar gasea are 

 formed within it, these will rapidly 

 exhale through all parts of the body ; 

 and hence the rapidity with which, 

 in certain states of disease, the sur- 



rounding atmosphere becomes tainted. 

 5th. The putrefaction of the interior 

 parts of a carcase will proceed as 

 rapidly as that of the exterior, from 

 the ready passage outwards of the 

 gaseous products. 6th. The exchange 

 of oxygen and carbonic acid in the 

 lungs is not prevented, but rather 

 promoted, by the intervention of the 

 membrane of the lungs and the coats 

 of the blood-vessels between the blood 

 and the air. It is necessary, however, 

 that there should be a substance in 

 the blood with which the oxygen of 

 the air may immediately combine ; 

 otherwise, instead of passing into the 

 blood, it would permeate the whole 

 organism : and it is necessary that the 

 carbonic acid, as formed in the capil- 

 laries, should also find a substance in 

 the blood with which it can combine ; 

 otherwise it would leave the body at 

 all points, instead of being discharged 

 through the lungs. 



§ 5. The following is a deduction 

 which confirms, by explaining, the 

 empirical generalisation that soda 

 powders weaken the human system. 

 These powders, consisting of a mix- 

 ture of tartaric acid with bicarbonate 

 of soda, from which the carbonic acid 

 is set free, must pass into the stomach 

 as tartrate of soda. Now, neutral 

 tartrates, citrates, and acetates of the 

 alkalis are found, in their passage 

 through the system, to be changed 

 into carbonates ; and to convert a 

 tartrate into a carbonate requires an 

 additional quantit}' of oxygen, the 

 abstraction of which must lessen the 

 oxygen destined for assimilation with 

 the blood, on the quantity of which 

 the vigorous action of the human 

 system partly depends. 



The instances of new theories agree- 

 ing with and explaining old empiri- 

 cisms are innumerable. All the just 

 remarks made by experienced persons 

 on human character and conduct are 

 so many special laws which the gene- 

 ral laws of the human mind explain 

 and resolve. The empirical generali- 

 sations on which the operations of the 



