198 George's Cause of Dry Hot. 



Whether simple heat ever exists in a concrete, visible, and ponderous 

 form is at least enigmatical. That it is a principal agent in the combination 

 and dissolution of matter is obvious and well known ; but that it should 

 disengage any former!}' combined portion of itself existing in a cellar door, 

 or lower timbers of a ship, while the baker's peel, or mantle shelf over a fire- 

 place, remains uninjured, is not so easily understood. Were it asserted that 

 it dissolves and dissipates the resinous qualities which give adhesiveness and 

 tenacity to the fibril tissue or structure of the timber, the explication would 

 be at least plausible; but that there is such a thing as neutralised heat, and 

 r.s such combined with resin, and which becomes fugitive in some cases 

 (though not in all), on receiving an active current of itself, is not easily 

 comprehended. Many would say, in the case of the door, that it was 

 ptiinted too soon, and before the deal of which it was made was thoroughly 

 drained of its aqueous sap. This sap being confined by the impermeable 

 coats of paint, would naturally be excited into a destructive fermentation by 

 the current of heat, and in time cause rottenness. This is the way in which 

 many would account for the destruction of the door ; but this is presup- 

 posing a case which there is no ground for beheving existed; and as the 

 author does not consider an explanation of the manner of the destruction 

 necessary, so we consider it altogether unnecessary to express any thing like 

 scepticism as to the truth of his conclusions, or of the value of a discovery 

 which promises such great and manifold advantages. 



There is one omission, however, in the account of the cella" door, which, 

 had it been added, would have been strongly corroborative of the validity 

 of the author's discover)', viz. whether the upper or lower part of the door, 

 first began to decay. According to this gentleman's observations (and they 

 are naturally faithful), the greatest quantity of heat, both in degree and ra- 

 pidity, passed and repassed the upper part of the door; in course, if heat be 

 the destroyer, this must have been damaged some time before the lower part. 

 The author treats the notion of those who believe that the dry rot is 

 caused by a fungus, as he says himself, " rather unceremoniously." (p. 46.) 

 But here he betrays some want of knowledge as a naturalist. Can he be 

 ignorant that the almost invisible roots, if such they may be called, of this 

 occult tribe of vegetables, have the power of changing the colour and con- 

 slitution of both mineral and vegetable bodies, without showing any external 

 sign of their existence ? While the filaceous structure of even the common 

 mushroom, one of the most palpable of the tribe, is luxuriating in darkness, 

 and dry heat, decomposing the consistence, and devouring the colour and 

 qualities of the soil in which it is placed, not a vestige of its fructification is 

 to be seen on the surface. This does not appear till long after the plant 

 has full possession of the place ; and no doubt many instances of unac- 

 countable spontaneous decompos't'on, are caused by invisible funguses which 

 have never yet been detected by the naturalist; so minute is their organi- 

 sation ; their existence being only suspected from a view of their effects. 



The cure for this great and, by all accounts, increasing evil, the author pro> 

 poses to accomplish by a new and ingenious mode of effective ventilation. 



By the apparatus described, and the manner of working it by indications 

 of thermometers, an equality of temperature may be maintained in the 

 deepest recesses, as in all other parts, of a ship or house. An equal degree 

 of heat on all sides will pervade the whole fabric, so that this subtle ele- 

 ment will never be attracted by colder substances, nor any transmission of it 

 from place to place kept up. For instance, if, as is usually the case, the 

 -water in which a ship floats is colder than the confined air of the hold, the 

 cooled planking of the sides will naturally attract the interior heat which 

 will pass through outwards leaving condensed, on the inner surface, the water 

 ■vvhich it holds in solution. In this case, the thermometer in the hold will 

 indicate the disparity, and the engine man will immediately pump out the 

 WHi'mer air of the hold, to admit a volume of colder air to descend in its 



