By Sir George Stewart Mackenzie, Bart. 177 



P. S. Since writing the above, it has occurred to me, on 

 seeing the old observatory here taken down, that by making 

 the glass semi-dome in two parts, and placing it on rollers in 

 the manner of an observatory dome ; the whole might be 

 moved with great ease and safety, so as to expose the whole 

 of the plants in the interior to the direct influence of the sun, 

 when that may be thought expedient. Thus the only diffi- 

 culty, in the way of constructing a house of a spherical form, 

 seems to be removed. But if experiment shall prove that a 

 circulation of air is of greater importance in the ripening of 

 fruit, than the loss of a portion of the sun's rays ; the expense 

 of this movement, as well as considerable expense in the 

 ordinary construction of hot-houses, may be avoided. 



