498 Dinbur Castle^ its Gardens and Gardeners. 



He will also find it useful at times to be able to explain the laws 

 by which the elementary particles act on each other, and also the 

 combinations or decompositions resulting from the affinity of their 

 ultimate elements, the nature of rocks, and the formation of soils. 

 The best botanical systems, vegetable physiology, and many other 

 branches of natural history, will be found extremely useful to the 

 intelligent gardener. Young men may also derive much plea- 

 sure and advantage by studying the art of drawing ; its founda- 

 tion is laid in geometry and perspective, and the study of both 

 is necessary towards the attainment of the art. Many may ima- 

 gine that such a variety of subjects may be unnecessary for the 

 gardener to know ; but it could be easily shown how important 

 thev all are, and others besides those already mentioned, in the 

 way of his profession. There appears to be a mutual dependence 

 of one branch of knowledge upon another; and the various 

 branches of science are blended with each other in such an 

 intimate manner that many discoveries in one department of 

 knowledge would probably never have been made, unless they 

 had applied to ascertained facts and properties resulting from 

 others. The astronomer, in order to find out the true position 

 of some of the heavenly bodies, has many corrections to make, 

 such as the correction of refraction, of the parallax, of nutation, 

 and aberration ; and, to be able to make the correction of re- 

 fraction, he must go to the sciences of optics and pneumatics, 

 and often the knowledge of one fact leads to the discovery of 

 another. The true length of a degree of the meridian established 

 Sir Isaac Newton's theory of universal gravitation. 



" The working out of the arrangements that may be entered 

 into this night will, I have no doubt, be the means of increasing 

 your acquaintance with much that will prove advantageous to 

 you all in future days. The giving away of knowledge is per- 

 haps different from the giving away of any thing else : he who 

 parts with it to others may do them much good, and become 

 none the poorer himself; on the contrary, he understands his 

 subject better, and is prepared to make new voyages in unknown 

 regions. The plan I would advise you to follow is a very simple 

 one, but I believe will prove a useful one. Let one take a sub- 

 ject of which he has already some knowledge and write a short 

 essay ; make it as plain as possible, in order that those who are 

 ignorant of it may be enabled to understand ; and, when it can 

 be done, make experiments, and show diagrams or models, that 

 the thing may be clearly understood as you go along. After the 

 essay is read, let a general conversation take place on what has 

 been delivered, and questions may be put and answers given 

 when it can be done. Many are afraid to make enquiries after 

 things, for fear of their ignorance being known ; never let such a 

 false delicacy influence your pursuit after such as are useful, 



