544- General Notices. 



retarded by their opposites. The mean duration of life has gradually in- 

 creased in England, and even more strikingly in cities than in rural districts, 

 since statistical tables were kept. In the middle of the last century, the 

 annual mortality of London was about one in twenty ; by the census of 

 1821 it is as one in forty. On the continent of Europe similar changes 

 have been taking place, but in a very inferior degree. A great portion of the 

 deaths in cities is assigned to the constant importation from the country of 

 individuals who have attained to maturity, but who having been previously 

 habituated to frequent exercise in a pure atmosphere, and to simple regular 

 diet, are gradually sacrificed to confined air, sedentary habits, or a capri- 

 cious and over-stimulating food. A large portion of the disease of the 

 country population arises from the excessive use of spirituous liquors, or of 

 low sour wines or ciders. Masons are most subject to consumptions, and 

 tanners least so : soldiers are more healthy than sailors ; there is more dis- 

 ease in an army during an unsuccessful than during a successful campaign : 

 gardeners and agriculturists, who have families, produce somewhat more 

 male than female children, and the contrary as to those who are engaged in 

 the pursuits of commerce and manufactures. Improvements in the public 

 health are uniformly attended by a diminution of marriages and births, 

 because there being only a certain quantity of subsistence, if men live 

 longer, there must be a smaller number of them produced. Thus, with an 

 equal mass of living beings, there is a smaller drawback by^deaths and the 

 pains and dangers of child-birth. — Cond. 



Heating by hot Water. — Mr.Weekes, manufacturer of horticultural build- 

 ings in the King's Road, has made one of the greatest improvements which 

 have been accomplished in this mode of heating since its application to gar- 

 dening purposes. One of the few objections to the system has hitherto been, 

 that, in a cold morning, the temperature of a forcing-house cannot be so 

 suddenly raised, and in foggy weather the damp in a green-house cannot be 

 so suddenly dried up, as by fire flues. Mr. Weekes has completely removed 

 this difficulty, by circulating the water along a box or tube, 12 or 1 Sin. broad, 

 and only |^in. deep, inside measure. The^boiier being small, and exposing 

 a long surface to the fire, on Mr. Cottam and Mr. Fowler's principle, the 

 water is soon heated, and passes rapidly along the broad tube {fig. 110. a a), 

 which, exposing 2jq 



so large a sur- f)==r^ — — ~ 



face, quickly c?//°/ 

 gives out its 

 heat. At the 

 further end of 

 the house this 

 broad plate is 

 connected with 



two returning pipes ; one of a very small diameter, barely sufficient to carry 

 back the water sent forward in the broad tube {h), and the other of 6 in. or 

 a foot in diameter (c), to serve as a reservoir of heat in the night-time, or to 

 be employed instead of the small returning pipe, when the house is once 

 heated to the proper degree. The returning pipes open into a small cis- 

 tern (c?), formed in the end of the broad tube, and the opening to each pipe 

 is stopped by a plug ; the one or the other of which is taken out, according 

 to the tube the water is meant to return by. Nothing can be more beautiful, 

 simple, and effectual, of which any one may be convinced, by inspecting the 

 apparatus, placed in a house 60 ft. long, on Mr. Weekes's premises. Of 

 course, the direction of the pipes may be varied at pleasure, to suit every 

 form of house ; and instead of a returning pipe of large dimensions, a second 

 one, of small diameter, might pass through a series of cisterns, of such 

 dimensions as would retain the heat for any term considered necessaiy. To 

 retain a layer of water on the upper surface of the broad tubes, for the 



