xxii 



Proceedings. 



In reference to the paper of Mr. Hodgkinson, a letter was read 

 from E. B. Smyth, Esq., one of the hon, secretaries, who was 

 unable to attend. 



Melbourne, July 9th, 1855. 



Dear Sir — I have to thank you for having permitted me to peruse a 

 manuscript of yours on the soils, and general agricultural properties of 

 the lands in Victoria. You have handled the subject so carefully, and 

 displayed such a large amount of practical knowledge in that department 

 of science, that I dare not venture to offer a criticism. 



Your analysis of the volcanic soils is borne out by the facts elicited by 

 Klaproth, Vauquelin, Rose, and others, in reference to the minerals 

 which these rocks contain ; and you have done great service to agricul- 

 ture by pointing out the causes of the remarkable fertility of soils of 

 such a character. 



Let me offer a few remarks, in addition to what you have stated in 

 your paper, in elucidation of the facts there put forth. 



One great cause of the fertility of volcanic soils is due to the colour, 

 consistency, and the consequent comparative rapidity with which such 

 soils radiate heat absorbed during the daj'-. Experiment has shown that 

 the general temperature of rich black mould is some degrees higher than 

 wet clay during the solar heat ; and a regular scale of temperatures is 

 found between white clay saturated with moisture and black earth. Now, 

 in addition to this, it is found that a rich black soil, radiating heat as it 

 does with such rapidity, necessarily condenses a larger amount of dew 

 than a clay soil, thus supply the plant with an absolute necessary in com- 

 parative abundance. This property is really an objection in a climate 

 such as England, if in excess ; but in this climate it must be held as a 

 prime consideration in choosing land for agricultural purposes. 



I do not hold that this applies in strictness, or with equal force, to all 

 volcanic soils. It is, however, the characteristic of the volcanic soils iu 

 this country. For the growth of cereals — wheat for instance — where 

 the roots are fine and radiating, and the stalk high and heavy, possibly 

 volcanic soil of the richest kind is not to be chosen. It is perhaps better 

 adapted to horticultural products. 



Another cause of the fertility of this soil is to be found in the vast 

 amount of decaying and decayed vegetable matter which it contains. — 

 This, I need not remind you, has the property of absorbing carbonic 

 acid from the atmosphere, and in itself, almost indestructible, is a never- 

 failing storehouse for this essential ingredient in vegetable substance. — 

 When engaged in experimenting in England, in 1850 and 1851, I re- 

 peatedly raised crops from pounded charcoal. The plants were kept in 

 pots, regularly watered, and subjected to different temperatures, and the 

 results were most satisfactory. I may venture to say that almost any 

 soil may be rendered productive by the addition of pounded charcoal, or 

 coal dust, or soot. 



It is the vulgar opinion of agriculturists that charcoal in this shape is 

 really appropriated by the plant, but this is now utterly exploded where- 

 ever experiment has taken the place of vague conjecture. 



Having devoted a considerable portion of my leisure time in England, 

 some three or four years ago, to the consideration of these questions, 



