375 



f^Toqeedingi at the Friday Evening Meetings of the Members 



IB fu /Jil.jJ'i of the Royal Institution, 



March l'2th. 

 In the Lecture-room Mr. Brande gave an account of the chemical 

 composition of urinary calculi, principally with a view of illustrating 

 the medico-chemical treatment of the disease, and of pointing out 

 iike great importance of attending to it in its early stages, at which 

 period it is too frequently neglected. The appearances of the urine 

 connected with the formation of white and of red sand were particularly 

 described, and the acid and alkaline plans of treatment explained, in 

 :<eference to the morbid secretion of the phosphates, and of uric acid, 

 • and to the prevention of the concretion or agglutination into calculi. 



March 19 th. 

 Mr. Ritchie, On the Methods which have been proposed for measure 

 ing the relative Ititemities of Natural and Artificial Lights. — In a 

 few introductory remarks, Mr. Ritchie exhibited the rise and pro- 

 gress of this interesting department of optical science. He ob- 

 served, that men had been accustomed to look at the sun, moon, 

 planets, candles, lamps, &c., for an unlimited period ; yet it was not 

 till the year 1730 they had formed any definite idea with regard to 

 the relative quantities of light afforded by these various sources. In 

 the year 1730, the celebrated Bouguer published his ingenious little 

 work, entitled, " Essai d'Optique," and in 1760 he completed what 

 was imperfect in his first essay, in his elegant work, entitled " Traitd 

 d'Optique sur la Gradation de la Lumiere." About the same time, 

 Lambert, whose name is well known to the scientific world, 

 published his profound physico-mathematical work on the Meli- 

 suration of Light, to which he gave the name of " Photome- 

 tria," or the art of measuring light. Nothing more had been done 

 towards the advancement of this interesting and useful subject till 

 Count Ruraford re-invented the method of shadows, described by 

 Bouguer, in the introduction to his " TraittJ d'Optique." So little, 

 indeed, was the ingenious work of the French philosopher known in 

 this country, that the method of shadows, as it is commonly called, 

 was for a long time considered as the invention of our indefatigable 

 countryman. That Count Rumford invented the method of shadows, 



