620 Retrospective Criticism. 



while the sun is shining and clouds are floating along the lower fields of 

 ether, to observe the time the shadows of the clouds move over known 

 distances. 



The exact velocity of the wind may, of course, be measured by means 

 of a small balloon, regulated, as near as possible, to the weight of the 

 lower atmosphere, or by a few down feathers, attached together by light 

 threads, forming an open tuft. This plan would require two operators on 

 a large open field, placed at a measured distance from each other in the 

 line of the wind, with muskets or flags to make signals to ^ach other. The 

 minutise of doing so need not be described. It has been attempted to 

 construct a measure of the velocity of wind by measuring its impelling 

 power (momentum) ; but, as the impelling power is the product of the 

 density and velocity, some means of estimating the correction for the greater 

 or less density is requisite. Were the density estimated under the different 

 temperatures and atmospheric pressures, an anemometer on this principle 

 would probably be the most convenient and correct. I have often found 

 a cold freezing wind have greater momentum upon the sails of a vessel, than 

 a warm summer wind, apparently to the senses, of no less velocity. — 

 Author of " Naval Timber " [see p. 78.]. May 17. 1831. 



Eschschbltzia. californica a hardy Perennial^ and Yerbena chavusdrifolia 

 almost hardy. — Sir, I have pleasure in confirming your statement, p. 342., in 

 your review of Maund's Botanic Garden for March last, that the Esch- 

 scholtzza is of perennial duration. A seedling plant flourished and flowered 

 very luxuriantly with me last year, and in November I covered it over 

 with dry straw: in February last I uncovered it, and found it already 

 about to leaf. It is now a very fine. plant, and will very shortly be in 

 flower again. I have several fine seedlings raised this spring some I 

 will leave unprotected through next winter, to see if they will survive, as 

 you have known them do ; and others I will plant on rockwork, to the end 

 you suggest. Ferbena chamaedrifolia, also, survived last winter, with only 

 the protection applied to the EschscholtzJa. I am, Sir, yours, &c. — Thomas 

 Edgeworth. Wrexham, June 8. 1831. 



To "planting" we greatly prefer sowing the Eschscholtzia at once 

 where wanted (not even in pots, to be thence turned out), and discarding 

 the supernumerary plants as they arise : one at a place is sufficient. The 

 plant has a fleshy, perpendicular, spindle-shaped rootstock, and, like many 

 plants so circumstanced, is so checked by ti'ansplantation, as to occupy 

 days, and sometimes even weeks, in recovering. This loss of time, and the 

 miserable aspect of the plant during this time, are both prevented by the 

 inconsiderable expense of a few additional seeds, and the timely thinning 

 out above recommended. — J. D. 



The Monteath Pear. — Sir, In reply to Mr. James Smith's remarks 

 on my account of the John Monteath pear tree at Orniiston Hall ( p. 239.), 

 I have to thank him for the tender concern he manifests about my " feel- 

 ings," and to assure him that they are still unhurt by his remarks. 



" A moral, sensible, and well-bred man 

 Will not affront me, and no other can." 



Had Mr. Smith applied to me for an explanation before he sent his remarks 

 for publication, I would have referred him to the polite and intelligent 

 gardener at Ormiston Hall (Mr. Pearson); to whom, I have no doubt, it 

 would have afforded much pleasure to have communicated, either to the 

 " noble Earl of Hopetoun," to His Lordship's gardener (Mr. James Smith), 

 or to the noble lady, his correspondent of" Oct. 1830," the same particu- 

 lars which he very obligingly communicated to myself and friends ; the 

 substance of which formed the whole of my communication respecting that 

 pear-tree : and I think it would be difficult to point out how any person 



