490 Retrospective Criticism. 



has been published, in which is a notice of a steam-plough, projected by Mr. 

 Dickson, Engineer, 9. Charlotte Street, Blackfriars' Road, London. Mr. 

 Dickson says, " About the time that the Leeds railway was done, when high- 

 pressure engines were much improved, the idea of thrashing by steam led me 

 to think of making a portable plough, applicable to all kinds of land. Now 

 that public companies are forming that will require the use of such things, 

 perhaps my old plan may be useful to some of them." (^Mech. Mag., vol. xxv. 

 p. 290.) 



Mr. Dickson adds that, perhaps ere long, steam-ploughs will be " going 

 about, and undertaking to plough fields for whoever may desire their assist- 

 ance, and with very little more preparation than is now required to place a 

 portable thrashing-mill :" which reminds us of similar ideas expressed by us in 

 this Magazine for 1828, vol. iii. p. 242 — 244. To this article we beg the at- 

 tention of such of our readers as are interested in the application of steam 

 power to the cultivation of the soil. 



The Edinburgh Chronicle states that Mr. Alexander Craig of Carlton 

 Street, Edinburgh, has taken out a patent for an American steam-plough, 

 which costs much less than Mr. Heathcoat's, but, probably, is not sufficiently 

 powerful for bogs. " The steam, generated in a boiler, passes out through a 

 tube leading into a tubular horizontal shaft : on opposite sides and near the 

 extremities of which are two apertures through which the steam escapes. The 

 revolving shaft is contained within a cylindrical casing, and turns, when in a 

 proper state of action, about 3000 times in a minute, on exactly the same 

 principle as Barker's mill. It is so simple, that it can be put up and kept in 

 operation by any man of ordinary ingenuity. The running part consists of 

 but one piece of cast steel, dispensing with cylinder, piston, valves, crank, 

 and fly-wheel : and hence its great cheapness." (Morn. Chron., Aug. 8.) 



Art. IV. Retrospective Criticism. 



ANALYSlsof Vegetables and Manures. — Having read, in p. 319., some remarks 

 on the value of bones as a manure, and some account of their component 

 parts, specifying that they contain a considerable portion of carbonate and 

 phosphate of lime, I consider this paper to be only a seed sown which may 

 produce abundance of useful information, both to the horticulturist and agri- 

 culturist. If some of your correspondents, who have the opportunities and 

 time to devote to, and who would feel pleasure in, the experiment, were to 

 analyse all the different sorts of vegetables in general use, stating the different 

 matters they contain, and the component parts of the different manures, &c. ; 

 and, also, if it is to be understood that those manures should be used which 

 contain the greatest portion of the same matter as the vegetable to be grown, 

 &c. ; it would be of the greatest use. Besides this, it should be stated what 

 influence the different ingredients have on the vegetables ; such as how saline 

 matters, phosphate of lime, carbonate of lime, magnesia, chalk, oil, &c., 

 operate. 



If this were well managed, so as to appear in a small pamphlet, and at a 

 little money, it would be very useful : not to spin the thread to a great length, 

 for the advantage of the book-maker, and the puzzling of illiterate men's 

 brains. A man who is not in the habit of reading is frightened at the first 

 sight of a large book. — J. D. Parks. Dartford Nursery, Kent, July 24. 1836. 



Variegated-leaved Plants. — I quite agree with you, that too much attention 

 is paid by cultivators to diseased varieties. I hate all variegations : they look 

 unwholesome, and always give me the idea of having been eaten and brought 

 up again. Even the variegated holly, I do not admire. — W. T. B. Allesley, 

 Dec. 5. 1835. 



The Formation of Arbor etums. — The perusal of the remarks contained in 

 this Magazine, on the formation of arboretums, has suggested to me the idea 

 that they might be rendered of immense practical utility as regards the intro- 



