428 Mr. Haworth's Binary Arrangement 



the process is much longer and more tedious on steel than on 

 copper ; yet, when completed, it is so perfectly satisfactory as 

 fully to reward the additional labour. The instruments used 

 in engraving in mezzotinto upon steel are precisely the same 

 as those employed in engraving upon copper. When a deep 

 black is required, twice the number of ways will be found de- 

 sirable ; from sixty to a hundred will not be too many. Steel 

 plates are now so well prepared, and are become so common, 

 that they are easily obtained by all who desire them ; the best 

 are those manufactured by Mr. Rhodes, and Mr. Hoole, of 

 Sheffield, who have paid every attention to rendering them fit 

 for the purpose of the artist : they may also be had of Mr. 

 Harris, Siioe-lane, London. 



I believe that I shall not be thought to entertain an erroneous 

 opinion, when I express my belief that it is solely to the intro- 

 duction of engraving upon steel into this country by Mr. Per- 

 kins, that we are indebted for the present successful applica- 

 tion of the same metal to the art of engraving in mezzotinto. 



In conclusion, it may be serviceable to add a warning and 

 receipt, which the novelty' of the use of steel in the art of en- 

 graving somewhat imperiously requii'es : — Great care should 

 be taken to save the steel from rust, which is done by warm- 

 ing the plate, and rubbing sheep's suet (from the animal) over 

 it, and keeping it near a fire, or in a dry room ; without this 

 precaution much mischief will arise. 



LXVIII. Observations on the dichotovious Distribution qt Ani- 

 mals: together xvith a Binary Arra7igcmcnt of the Natural 

 Order Saxifrageae. By A. H. Hawohth, Esq. F.L.S. t^r. 



To the Editor of the Philosophical Magazine and Journal. 

 Sir, 



SINCE my last communication to you, I have seen for the 

 first time (viz. June 3, 1825) a work entitled Zoologie Ana- 

 liliquc, by A. M. Constant Dumeril, printed at Paris in 1806. 

 It was lent to me by my friend Mr. H. Boys, one of the Fellows 

 of the Linnaean Society ; and it distributes the genera of ani- 

 mals in a method so allied to my own binary one, that it may, 

 perhaps, be said by some, that 1 have borrowed largely from 

 it witliout any acknowledgement. Wherefore it becomes ne- 

 ccssarv that I should assure the readers of your Magazine to 

 the contrary ; and that it was in consequence of my explaining 

 what I thought the complete novelty of my plan to Mr. Boys, 

 that he showed and lent me the ingenious and elaborate work 

 of Dumeril, as above stated. But I have not yet seen the bo- 

 tanical publications which that author mentions in his preface, 



although 



