Chemical Philosophers assert indeed--that a Gallon of the unsavoury Gas from Garlick Hill, gives as high a proportion of _Oxygen_, as the like quantity of the ethereal element of Primrose Hill:--this seems incredible, and must arise either from the imperfection of the _Eudiometer_ giving erroneous results, or from the air being impregnated with matter unfriendly to Health, which the instruments employed to analyze it, have not the power of denoting:--let any one thread the mazes of a crowded city, and walk for the same space of time in a pleasant Country--the animal spirits will soon testify, which is the most exhilarating. However, people certainly do live long, and enjoy Health, in situations apparently very unfavourable to Animal Life. Our Omniscient Creator has given to our Lungs, the same faculty of extracting nutriment from various kinds of Air--as the Stomach has from various kinds of Aliment:--the Poor man who feeds on the coarsest food, is supported by it in as sound Health, as the Rich man who fares sumptuously every day. Well then, in nine cases out of ten, to change the Atmosphere we have been long accustomed to, is as unadvisable as a change in the Food we have been used to--unless other circumstances make it so, than the mere change of Place. The Opulent Invalid who has been long indulged with a Home arranged to his humour--must beware (especially during any exacerbation of his infirmity) of leaving it--it would be almost as desperate a procedure as to eject an Oyster from his Shells. EXERCISE. "By ceaseless action, all that is subsists, Constant rotation of the unwearied wheel That nature rides upon, maintains her health, Her beauty, her fertility. She dreads an instant's pause, And lives but while she moves."--COWPER'S _Task_. "The wise, for Health on EXERCISE depend; God never made his work for Man to mend." The more luxuriously you live, the more Exercise[49] you require,--the "_Bon Vivant_" may depend upon the truth of the advice which Sir Charles Scarborough gave to the Duchess of Portsmouth, "You must Eat less,--or take more Exercise[50]--or take Physic,--or be Sick." Exercise is the grand power to promote the Circulation through the capillary vessels, by which the constitution is preserved from obstructions,--Appetite increased, and Digestion improved in all its stages,--the due distribution of nourishment, invigorates the Nervous System, gives firmness and elasticity to the Muscles, and strength to every part of the System. Exercise, to have its full effect, must be continued till we feel a sensible degree of _Perspiration_,--(which is the _Panacea for the prevention of Corpulence_)--see page 50--and should, at least once a-day, proceed to the borders of fatigue, but never pass them,--or we shall be weakened instead of strengthened. Health depends upon perpetual Secretion and Absorption, and Exercise only can produce this.