Retrospective Criticism. 103 



from foreign specimens. — David Cameron. Birmingham Botanic Garden 

 Bee. 14., 1839. ' 



Proj)ortion of Hot-Water Pipe required for heating. — In the Gardener's 

 Magazine for 1839, p. 565., it is stated that the rule there given may safely be 

 taken by gardeners, &c. Nov/ this rule gives only one twentieth part enough 

 for stoves, and about one fourteenth part enough for green-houses. I speak 

 from experience and calculation. You will see the extravagance of the rule 

 by the following application of it. If the pipes that are about to be laid 

 down at Chatsworth, in the new conservatory, were laid in a common hot- 

 house, say 12 ft. wide, 12 ft. high at back, and 5 ft. at front, then, according to 

 the rule, they would heat green-houses extending over twenty-four acres ; and, 

 if the houses were in one line, they would be nearly eighteen miles long. — 

 Alexander Forsyth. Alton Towers, Cheadle, Staffordshire, Bee. 19. 1839. 



The Grand Conservatory at Chatstuorth, — In the Gardener's Magazine for 

 1839, p. 450., the Chatsworth Conservatory is said to be executed " with a 

 degree of taste, science, and economy that will surprise every one." Leaving 

 the science, elegance, &c., in abler hands, I only want to show you that the 

 ridge-and-furrow roof is not economical. I was not fortunate enough to see 

 Counsellor Harrison's ridge-and-furrow hot-houses at Cheshunt, although 

 I lived some years in that neighbourhood, which you praised so much in the 

 Gardener's Magazine for December, 1839 ; but I have seen the originals at 

 Chatsworth, and from them I will make my calculations : and, lest you or any 

 one should construe this into an ill-natured criticism on the works at Chats- 

 worth, I will just premise that I called there in the autumn, and experienced 

 the greatest kindness ; and was quite astonished at the extent, variety, and 

 high keeping of that most interesting garden. It is, therefore, the system of 

 building hot-houses in ridges and furrows that I object to, as being anything 

 but economical, and not against the princely garden structures erected by the 

 noble duke, under the direction of Mr. Paxton. It is a standing principle 

 among those who study economical hot-house-building, that a rood of glass 

 should roof a rood of ground, and, ergo, an aci'e of ground might be roofed 

 by an acre of glass. Now, let us take the new conservatory at Chatsworth 

 for an example, and suppose its section represented by a circle, of which the 

 side ailes are quadrants, and the centre aile a semicircle. It will thus form 

 a circle, whose diameter will be one half of the real width of the house. 

 Suppose, then, the diameter 1 ; then the width of the house will be 2, and the 

 circumference of the circle, or the length over the roof across the house, will be 

 3 ; and, at the lowest rate, the ends and extras will amount to one part more. 

 This gives just double the area of the floor, for a roof whose section is as 

 above. Now for the furrows ; and suppose them to form with the horizon 

 the three sides of an equilateral triangle, you will see that this just doubles it 

 again. So I conclude that, if this rough calculation be anything near the truth, 

 this roof would cover nearly four acres of glass, certainly not less than three, 

 to light and heat one acre of land ; and, leaving the circular section alto- 

 gether out of the question, the ridge and furrow alone would take twice the 

 glass necessary for a plain roof, which is found to answer every purpose quite 

 as well ; and, certainly, in houses of ordinary shape and size, like Mr, Harri- 

 son's, it is more simple and rational. — Idem. 



Parijig the Verges of Walks. — In different places in the Gardener's Maga- 

 zine, you say verges of walks should be clipped and kept green, and not pared 

 to the raw earth. Now this is not fair argument, because, when the verge is 

 deep enough to have raw earth so conspicuous, the walk wants more gravel to 

 raise it up to within 1 in. of the grass level ; and if the verges of walks thus 

 filled are not nicely pared every spring, as well to regulate the lines and curves 

 as to cut the roots of grass, which otherwise would intrude upon the gravel, 

 they would cause fifty per cent more labour to keep the walks neat through 

 the summer. A deep raw edge is detestable in a garden, and a deep green 

 edge is worse where labour is scarce, as it takes great labour to clip it, and 

 gives the walks a sunken and worn out appearance. Think not by this that I 



