892 



we should decide on the merits of a copious index to a voluminous publication, for the pur= 

 poses of both are the same : both are equally useful, and the merit of both lies in clearly 

 directing the reader to the precise point on which he desires information. A good artifi- 

 cial system is, therefore, not only a useful, but even, in some respects, a valuable inven- 

 tion, requiring much more skill than is generally supposed ; and it is, perhaps, much 

 more adapted for general use than any other. The most admirable classification of this 

 sort ever invented, is that denominated the sexual system of plants, by Linnaeus. Many 

 natural assemblages are preserved without any great violation of the principles on which 

 he set out. This is always a great recommendation to an artificial system, yet it is by no 

 means necessary to its formation. Natural affinities may be overlooked wherever they 

 interfere with precision of arrangement, the first are secondary, the latter primary. We 

 open an artificial system to come to the knowledge of a matter of fact ; but if we wish 

 to proceed farther, and to know how this fact bears upon other facts, we turn to the na- 

 tural system. Such are the uses of the two methods of classification upon which we 

 have been speaking, and such the theoretic distinctions by which they are separated. 

 Between them, however, is a third sort of system, which, from combining artificial di- 

 vision with some regard to natural affinities, are generally termed mixed systems, or 

 half-artificial methods, while others (and generally among this number are the authors 

 themselves), have pronounced them natural arrangements." 



I fear, Mr. Editor, that I have quite exhausted your patience, and 

 shall now subscribe myself, Your obedient servant, 



Ph. B. Ayres, M.D. 

 To the Editor of ' The Phytologist.' 



Art. CC. — An Account of a Visit to Teesdale in the Summer of IS4S. 

 By James Backhouse and James Backhouse, jun.* 



As an account of a visit made last summer by my father and myself 

 to Teesdale and some adjacent parts, may interest the readers of 'The 

 Phytologist,' I send thee some account of it. 



We set out on the 28th of 8th month, and proceeded by railway to 

 Darlington ; from thence we went to Bishop Auckland, where we left 

 the railway, and walked to Shull between Hamsterly and Wolsingham. 

 There we found Hieracium boreale, Scutellaria minor, Listera cordata, 

 Vaccinium Vitis-Idsea, Pyrola media and minor, Lastrsea Oreopteris, 

 Polypodium Phegopteris and Dryopteris, and Equisetum sylvaticura. 

 In the native birch-woods at this place, the broad and narrow leaved 

 varieties of Convallaria majalis occur; and a robust, upright and very 

 hairy variety of Veronica scutellata ? is found in ponds. Dianthus 

 Armeria occasionally springs up here, where the ling has been fresh 

 burned off. The day following we walked over the moors, by com- 



"* Communicated by James Backhouse, jun. 



