NATURAL PHILOSOPHY. 147 



\>e wafted by the slightest current. The tenacity of the film was 

 shown by allowing drops of water to fall through the bubbles, which 

 could be accomplished without breaking them. 



By dipping small wire cages, forming the outlines of geometrical 

 solids, into the mixture of oleate of soda and glycerine, plane films 

 were produced intersecting each other in various directions in the 

 interior of the wire frames. Many of these offered very remarkable 

 geometrical combinations; the wire outline of a tetrahedron, for 

 example, on being withdrawn from the solution, was shown to contain 

 six triangular films, all meeting at the centre of the figure. 



RUTTAN'S "EXHAUSTION" PRINCIPLE OF VENTILATION. 



Mr. Henry Ruttan has recently published in New York a work 

 designed to illustrate a peculiar system of warming and ventilating 

 dwellings, upon what the author calls "the exhaustion principle," 

 and which it is claimed has been applied with success on railroad 

 cars. 



On the subject of heating different houses, Mr. Ruttan states that 

 the difference of locality and size of different apartments in houses 

 is so great that it is utterly impossible to lay down any rule in the 

 generation of heat, but he gives the following advice, as derived from 

 experiment, respecting the heating of rooms in relation to their depth 

 between the ceiling and floor. He says : " People are generally im- 

 pressed with the idea that it is the ground area, or lateral measure- 

 ment of a room, by which they are to be guided in arranging for its 

 warming, but this is not correct ; it is the height by which they should 

 be chiefly governed. When I tell you that it takes about double the 

 quantity of fuel to warm a room twelve feet high that it takes to 

 bring one of the same lateral measurement and ten feet high to the 

 same temperature, you may be surprised, yet this is a fact which I 

 have proved by many experiments." In another place he says : 

 " We must have no rooms over ten feet high, and nine feet would be 

 better, except in the cases of churches and theatres, where special 

 provision is made for warming. I know there will be strong opposi- 

 tion to any such proposition, for hitherto high ceilings have been 

 looked upon as a sort of substitute for ventilation, and as the need 

 of ventilation was felt more in cities than in the country, the ceilings 

 of apartments were made higher there, and from this it has grown 

 into the fashion. But if thorough ventilation can be secured, the 

 great advantage a low ceiling possesses over a high one in the saving 

 of fuel, as well as in the rapidity of a change of air, will, I think, 

 induce those people who are governed by common sense to adopt it. 

 That this thorough ventilation can be secured, there is not a shadow 

 of doubt." 



As it respects the forms of hot-air furnaces, Mr. Ruttan asserts 

 that those manufacturers who increase the heating surface of their 

 productions by pipes, corrugated, or otherwise, act upon unphilosoph- 

 ical principles. The best shape of an " air-warmer" for buildings, he 

 says, " is that which presents the greatest surface to the centre of the 

 fire, and that being globular, this is the form most efficient and 

 economical for warming houses by air." And to sum up the question 



