Meteorological Journal at Beloit, Wis. 241 
Two of the best goniometers used for this purpose are those of 
Ross and Leesom, the latter being doubtless the best, and based 
on the use of the double refracting spar. After trial, however, 
I find it neither as accurate nor as economical in its construction 
as the following :— 
Around the tube N, fig. 1, there is a collar X fastened to it; on 
the collar there is a graduated circle S, about three inches in 
diameter, turning freely on X. On the tube G a small index ¢ is 
fastened. These are all the additional parts necessary, as the 
micrometer just described is used to aid in the measurement, 
which is accomplished as follows: The angle of the crystal to 
be measured is brought as near the centre of the field as the eye 
can readily judge of, (a little deviation will not sensibly affect the 
Measurement); the micrometer is then introduced in the opening 
-g,and turned about until the lines are parallel to one side of the 
angle, or until one of the long marks correspond with that side ; 
this done, without disturbing the tube G, the graduated circle 5 
‘Is turned, until the index ¢ points to zero. Now look again into 
the instrument, and turn G until the markings on the micrometer 
are parallel with the other side of the angle ; read the number of 
ees on the circle, and this will be the angle or its compliment. 
It frequently happens that the micrometer has to be moved in or 
out to make the lines on it accord with the second side, but.as this 
motion is altogether a parallel one, the accuracy of the measure- 
. Ment is not at all effected. ‘The simplicity of the mechanical 
arrangement is readily seen; the same advantage in using t 
micrometer with every eye-piece belongs to the goniometer. 
=—=— 
Arr. XXVIIL.— Abstract of a Meteorological Journal, kept at Be- 
loit Colleze, Beloit, We: for the year 185t. Lat. 42° 30’ 23” 
N., long. 12° 03’ 20” W. from Washington : elevation above 
Lake Michigan, 172 feet—above the ocean, 750 leet; by 8. P. 
Laruror, M.D., Professor of Chemistry and Natural History. 
aaa rrr Remon 
: THERMOMETER. | Prevailing |Inches rain & 
— a Mean.}Max.| Min. Mean. yen oad winds. jmelted snow. 
January, 56 |-19124°72 5:04 wiw. & 8. are 
{brey, 35| 03807) 520 | s&x. | 348 
April eR a bie Rahs 2°35 
ae io “ ced 550 |s.£. &N.w. 15:46 
June, g8| 44 (6940 | 585 jnwedsw) 552 
July, 95 | 46 |71°84 648 s.w.d NW. 552 
August, o8| 50jo8es | 550 [sends | 086 
September, |29-68 94 | 32166:90 | 682 |[sw.dsx. vi 
‘October, 76| 20-491 | 612 .. & N. e40 
November, |29-89 43| 16 (9488 | 285 |x&s.w) 163 
December, 156 [192270 | 4°56) w.ds.w BS 
bb oe 6 6) 98 |-19 \46°895 Bit 'XN.W.& 8 55.90 
31 
Szcowp Serms, Vol. XIV, No. 41.—Sept., 1852. 
7 
