THE» 



EDINBURGH NEW 

 PHILOSOPHICAL JOURNAL. 



Fifth Letter by Professor Forbes on Glaciers, Addressed to 

 the Right Honourable Earl Cathcart. Communicated by 

 the Author. 



Rome, 29fA January 1844. 



My Lord, — In reply to your kind letter of the 14th De- 

 cember last, requesting me to communicate to the Royal So- 

 ciety any observations upon glaciers which 1 was enabled to 

 make during last summer, I may mention, that the state of my 

 health was so indifferent during the finer months of the year, 

 and the caution which it required so great, that I was quite 

 unable to prosecute as I had hoped the subject of my previous 

 inquiries in Switzerland. As, however, the journey was not 

 quite unproductive, I will very shortly state the additional 

 facts which I was enabled to observe, claiming from you and 

 from the Society the indulgence which their scantiness requires. 



At Chamouni, the most obvious consideration was to deter- 

 mine the actual annual motion of the ice, the partial motions 

 of which during the summer months had been carefully ascer- 

 tained by me, as stated in my former communications. For 

 this purpose, I had two marks of a permanently distinguishable 

 kind, namely, blocks of stone lying on the surface of the ice ; 

 the one, formerly marked D. 7, and referred to in my Travels 

 by that name, situated a little lower than the position of the 

 Montanvert; the other, marked C, or " Pierre platte," on the 

 Glacier de Lechaud, near its junction with the Glacier du 

 G^ant. It was the former of these masses which had been 

 approximately observed in position by my guide, Augusta 

 Balmat, during the winter of 1842-3, with great labour and 

 fidelity— observations which first conclusively proved the fact 



VOL. XXXVI. NO. LXXII. APRIL 1844. P 



