124 



and associated with stilbite. It was supposed by some to be hypo- 

 stilbite, but a quantitative examination gave the following results, 



Silicic acid, . . 53-048 



Alumina, . . . 22-943 



Lime, . . . 9-676 



Water, . . . 14-639 



100-306 



This analysis corresponds to that of Laumonite, but its formula 

 given by Gerhardt is not very satisfactory, 



3 Ca O, 2 Si O3 + 3 (Al^ O3, 2 Si O3) + 12 HO, 



Scolezite. — A mineral found in Mull, consisting of long radiated 

 needles, the composition of which was found to be, 

 Silicic acid, . . 46*214 



Alumina, . . . 27*0 



Lime, . . . .13-450 



Water, . . . 13-780 



100*444 

 corresponding to the formula of scolezite, 



Ca 0, Si O3 + AI2 O3, Si O3 + 3 HO. 



2. On a necessary Correction in the Height of the Earo- 

 meter depending on the Force of the Wind. By Cap- 

 tain Henry James, R.E. Communicated by Professor 

 Piazzi Smyth. 



During the frequent violent gales of last autumn, the author had 

 remarked the excessive fluctuation of the barometer ; and following 

 up this phenomenon by means of the portable aneroid barometer, 

 he found that not only was this fluctuation dependent on the wind 

 and on the barometer being in a screened position ; but that accom- 

 panying the fluctuation was a constant depression increasing in 

 amount with the velocity of the air, and that this depression amounted 

 in strong gales to a larger quantity than all the other usual correc- 

 tions applied to a barometrical reading; and must be applicable 

 to all the ordinary positions where barometers are observed, whether 

 by sea or land. 



The reason of this depression was then entered into, and the 

 amount of numerical correction was given, as depending on the 

 velocity of the wind, and the peculiarity of the exposure. 



