384 Proceedings of the Royal Institution. 



Dr. Clark^, On' the Ascent and Descent of Mont Blanc. — On a 

 former evening in the last season, Dr. Clarke gave an account of his 

 own ascent up Mont Blanc, and illustrated it by numerous paintings 

 and engravings, and by an abundant selection of specimens from the 

 animal, vegetable, and mineral kingdoms. On that occasion, he had 

 not time to enter so largely into the natural history of the mountain 

 and its neighbourhood as he desired, as will be seen by tlie report 

 given of it at p. 385, vol. v. of this Journal. On the present occa- 

 sion, he rapidly passed over the ground he formerly described, and 

 ^expanded upon those parts which were then merely noticed. As be- 

 fore remarked, we beheve that an account of the excursion will 

 shoiftly be made public in a separate form. 



May 1th. 



On the Measurement of a Base in Ireland, for the geodetical sur- 

 vey now in progress under the direction of Lieut.-Col. Colby. 



The subject this evening was delivered to the members by Mr. 

 Faraday, who was allowed the use of the apparatus constructed by 

 Messrs. Troughtonand Simms, for the East India Company, and was 

 instructed in the various parts of the subject, by Lieuts. Drummond 

 and Portlock, who have been extensively engaged in the measurement 

 of the base, and in the general triangulation. 



The objects contemplated in the survey of a kingdom may be 

 considered as twofold, and classed under the heads topographical and 

 geodetical. To the former belong the construction of maps and plans, 

 and the delineation of ground, conveying all the infonnation that 

 may be required for those local improvements, of which a knowledge 

 of the ground is an essential preliminary ; and serving at the same 

 tune as a basis for the valuation of the land, either confined to sub- 

 divisions of considerable extent, yet sufficient for the ]j)ti^j)i)6els^' of 

 taxation, or descending, like the cadaitre of Ftanci^, \6^^ii^'m6te 

 minute limits of private property. < "■• /a boaub , 



To the latter belongs the task of fixing the relative positib'h'i^ - of 

 places ; of assigning their latitudes and longitudes ; of connecting the 

 different observatories — an important object in astronomical science, 



