1828.] 



Proceedings of Learned Societies. 



been read in the years 1826 and 27, and 

 which, establishing the high reputation of 

 their learned author, have perhaps contri- 

 buted to his advancement to the situation 

 he at present occupies. 



SOCIETY. 



March 4. A communication was read 

 from the Rev. L. Jenyns, " On the dis- 

 tinctive characters of two British species of 

 plecotus, supposed to have been confounded 

 under the name' of long eared bat." A 

 new bat, found adhering to the bark of a 

 pollard willow, and which the author names 



539 



syis discriminated in this.memoir 

 from (icuitus, which, together with barbastel- 

 lus, make up Geoffrey's sub-genus plcc'itus 

 of the vespertilionidae. The difference in ab- 

 solute size, in the relative proportions of the 

 parts, in the colour, and in the apparent 

 habits, seem to require the making it a 

 distinct species. March 18. The death of 

 Sir James Edward Smith, who had held 

 the highly honourable situation of presi- 

 dent of this society from its first establish- 

 ment in 1788, having been communicated 

 to the meeting, it was immediately ad- 

 journed. 



VARIETIES, SCIENTIFIC AND MISCELLANEOUS. 



Achromatic Telescopes, During the lat- 

 ter part of the last century, the manufac- 

 ture of achromatic telescopes, which our 

 countryman Dollond had brought to such 

 perfection, was confined exclusively to this 

 country ; and although a limited, it was a 

 lucrative branch of our export trade, while 

 it extended the scientific character of the 

 nation. Fettered, however, by the opera- 

 tion of the excise laws, the English experi- 

 mentalists have been unable to make the 

 practical researches required for producing 

 flint glass of the necessary purity, in suffi- 

 cient quantities, or rather with a sufficient 

 extent of surface, to surpass in size the in- 

 struments made fifty years ago ; and, on 

 the continent, these researches have been 

 prosecuted with success, so that our trade 

 and our reputation, in this branch of art, 

 seem gone for ever. The magnificent in- 

 strument at Dorpat, made by Fraunhofer, 

 is well known. Mr. Lerebours, of Paris, 

 has now executed, from some of Guinand's 

 glass, an achromatic telescope, with an 

 aperture of twenty-four inches, and a focal 

 length of twenty-five feet ; and there are 

 at present for sale, in the French capital, 

 three object glasses, of six inches aperture, 

 and six feet focal length of seven inches 

 aperture, and seven feet focal length and 

 10'4 inches aperture, and seventeen feet 

 focal length. As a set off against these, 

 and the power of constructing similar in- 

 struments, the English must place the dis- 

 covery of Mr. Barlow ; we are happy to 

 have it in our power to announce the suc- 

 cess of this gentleman in the construction of 

 telescopes with a correcting fluid medium ; 

 and from his well known zeal in the cause 

 of science, we hope that he will not suffer 

 the effect of his valuable labours to be neu- 

 tralized by the proverbial cupidity of the 

 English opticians. 



Geography. We mentioned in our last 

 number, that, at the conclusion of this 

 year, two celestial maps would make their 

 appearance, far surpassing any which the 

 rest of Europe can boast j indeed the idea 



of giving them a rotatory motion, in the 

 plane of the equator, is one of singular 

 utility. The same spirited individual, Mr. 

 Arrowsmith, who has undertaken this 

 work, will shortly publish a comparative 

 atlas of ancient and modern geography, 

 from original authorities, and on a new 

 plan, for the use of Eton College. We may 

 express our surprise, that, considering the 

 necessity of geographical knowledge, (for 

 necessary it must surely be considered,) 

 so very few books on the subject, that 

 can be regarded as any thing more than 

 trash, are to be met with in England. 

 While, on the continent, the ablest profes- 

 sors do not think it beneath them to draw 

 up elementary treatises, here scarcely any 

 thing is to be met with but compilations, 

 " got up by the trade." 



Sand Vitrified by Lightning. M. Arago, 

 the French Astronomer Royal, presented, 

 last month, to the Academy of Sciences, 

 some tubes of vitrified sand, formed by 

 lightning, and of extraordinary dimen- 

 sions. Among the most singular effects of 

 lightning must be ranked the foraiation of 

 tubes of vitreous matter, which are found 

 on the highest mountains ; the mode of' 

 producing these tubes was for a long time 

 totally unknown. Philosophers are now 

 unanimous in ascribing them to the effect 

 of lightning, which, when it falls upon a 

 sandy soil, melts and vitrifies the sand to a 

 greater or less depth ; and this explanation 

 cannot be doubted, since similar tubes have 

 been observed to be formed instantaneously 

 in places where the lightning has fallen. 

 The vitreous tubes in question were col- 

 lected in Germany, in some sandy territo- 

 ries, and one of them is more than nine- 

 teen feet long. How the discharge of an 

 electric cloud could melt and vitrify so 

 thick a mass of sand is wonderful, when 

 the same effect could scarcely be produced 

 in our most powerful furnaces. 



Fate of La Perouse. The EastlndiaCom- 

 pany's ship Research having been despatch- 

 ed to the islands in the neighbourhood of 



3 Z, 2 



