ISogal Sn^titution of ©uat ISritain. 



WEEKLY EVENING MEETING, 



Friday, March 5. 



Sir Henby Holland, Bart. M.D. F.R.S. Vice-President, 

 in the Chair. 



Professor C. Piazzi Smyth, 



ASTttONOMEH-EOTAX FOR SCOTLAND. 



Account of the Astronomical Experiment of 1856, on the Peak of 



Teneriffe. ^ 



The object proposed in the astronomical experiment carried out on 

 the Peak of Teneriffe, the year before last, was to ascertain how 

 much telescopic observation can be improved, by eliminating the 

 lower third or fourth part of the atmosphere ; in other words, by 

 elevating instruments and observers some 10,000 feet above the 

 sea level. 



By such a proceeding, not only was it hoped to rise above the 

 greater part of the clouds, mist, haze, and other aerial impurities, 

 so patent to the eyes of all men, — but also to get rid of certain 

 other sources of optical disturbance, which only manifest themselves 

 to star-gazers, employing telescopes with high magnifying powers. 

 To such, those disturbances are rarely or never absent, even on the 

 finest nights ; and they act more and more prejudicially, the larger 

 and more perfect the instruments that may be employed. From 

 this cause it is, that the full magnifying power which a modern 

 telescope is calculated to bear, can very seldom be applied ; minute 

 celestial phenomena remain undiscovered ; and our opticians must 

 lose heart in carrying on the improvement of object-glass manu- 

 facture, if their best performances are to be for ever condemned to 

 have their finer qualities neutralized by the badness of the air in 

 which they are tested. 



Here is evidently an evil of no ordinary magnitude, and it has 

 troubled astronomers long. Clearly foreseen and carefully weighed 

 by Sir Isaac Newton, that great philosopher described the nature 

 of the difficulty, and the only means of remedy in 1730, in words 

 as felicitous as comprehensive. *' Telescopes," says he, " cannot 

 be so formed as to take away that confusion of rays, which arisen 

 from the tremors of the atmosphere. The only pemedy is a most 



Vol. II.— (No. 28.) 2 M 



