510 



MISCELLANEOUS GARDEN STRUCTURES. 



to prevent the sun from acting on the 

 sides. The annexed 

 Fig. 727. diagrams, figs. 727 



A. and 728, show the 



/ section and eleva- 



/ I 1 \ tion. The building 



x i a j s was erected, Mr 



— Smith assures us, 



\ for under £20, and 



\ / the timber used, 



\ / although the Earl 



\ / of Home's own, 



\ / was included in 



\ / the estimate at 



\ / the current price. 



^— r -r* The sides under 



\ / ground are not quite 



* ' perpendicular, al- 



though the house is described as being 

 square, — the slight batter being found, of 



Fig. 728. 



course, better resisted by the boarding 

 by which the sides are covered. 



A very economical ice-house has been 

 in use at Erskine House, the seat of Lord 

 Blantyre, near Renfrew. It consists of a 

 pit sunk in a gravel hill, 16 feet in 

 diameter at the top, 10 feet at the 

 bottom, and 8 feet deep. No drain is 

 here used, as the melted ice finds free 

 precolation through the gravelly soil. 

 Previous to putting in the ice, branches 

 of trees are laid across the bottom, and 

 over them some smaller spray, which acts 

 as a filter for the melted ice escaping. 

 When this pit is filled to about 3 feet 

 above the surface-level, the ice is covered 

 with from a foot to 15 inches of peat 

 earth, over which a temporary roofing of 

 spars is put, and slightly thatched. When 

 the ice is wanted for use, an opening is 

 made in the peat earth covering, and left 

 open during the season, the ice pro- 

 truding through the stratum of peat 

 earth, like a block of marble. Several 

 ice-pits upon the same principle exist in 

 different parts of Scotland. 



In this case we think the peat earth 

 will have the effect of discolouring the ice 

 very much — which, however, for the ordi- 

 nary purposes for which ice is used, can 

 be of little consequence ; but when re- 

 quired pure, to mix with water, wine, or 

 for being put into vessels containing 

 butter, &c, it must lessen its value very 

 much — nay, indeed, render it entirely 

 unfit for the purpose. In Britain we 

 have yet to learn the value of pure ice, 

 and the great necessity of collecting it 

 from clean sources. 



The oldest form of ice-house with 

 which we are acquainted is that of an 

 obovate shape — the shape which ap- 

 proaches the nearest to the spherical — 

 which of all other forms is the one best 

 suited to the purpose in view, because it 

 presents the least surface in proportion 

 to the cubic contents of the mass, and is 

 therefore much less acted upon by the 

 dissolving agents. And next to this is a 

 cube, amongst regular straight-sided 

 prisms. " If, however, a ball of ice — say 

 of 2 inches diameter— containing little 

 more than 4 cubic inches, be thrown 

 into tepid water along with a cube of 2 

 inches on the side, the latter, though 

 containing 8 cubic inches, will be melted 

 as soon as the spheric, which contained 

 but little more than one-half that quantity 

 of ice. But although nearly double the 

 quantity is thus wasted by the cube, as 

 compared with the sphere, yet this is little 

 to what will be found to take place in a 

 figure bounded by lines still less concentric 

 than the cube. Thus, from a flat piece of 

 ice 6 inches square by 2 inches thick, con- 

 taining 72 cubic inches, no fewer than 60 

 cubic inches will be dissolved in the same 

 time and by the same temperature that are 

 required to dissolve only 4 cubic inches, 

 when these are in the form of a sphere. 

 Although from this it is evident that the 

 most spherical form is that which is best 

 adapted for preserving a body of ice, 

 there are various circumstances, notwith- 

 standing, which render it necessary to 

 deviate from such in the construction of 

 ice-houses. The mass of ice, by solidify- 

 ing, and by partly melting at bottom and 

 top, when also a portion may be sup- 

 posed to be taken away for use, would 

 reduce the sphere to a flattened oblate 

 spheroid ; whereas the form of an oblong 

 spheroid, or that of an egg, the widest 



