W. Grunow— New form of Cathetometer. 23 
The experiments on the influence of the time of digestion, 
made with acid of 1°115, resulted as follows :— 
No. of Days Digested. 
Ingredients. 
1. 3 4. 5 10 
nsoluble residue, __.._- 76°97 72°66 71°86 70°53 W179 
oluble Silica,..._...._. 60 11:18 11°64 12°30 10°94 
DN oe oe 35 “44 57 63 “62 
oda, ... 06 06 03 09 28 
BAG ee os a ey 26 29 28 27 "27 
Js SESS reece eae hy) “44 “47 45 “44 
Tr. OX. Manganese, ____. “04 06 06 06 “06 
MnPO O20, 8 ore ATT 5-01 5-43 511 4°85 
cg ee eee 515 1-38 7-07 7-88 7-16 
Phosphoric acid, _______ 2 “21 
Sulphuric acid, ______ 2, 02 bade 
Volatile matter, _._____. 3:14 3-14 3°14 3:14 3°14 
Potable co a 99°63 100-68 100°55 100°69 99°80 
‘Amount of soluble matter.| 19-67 24°88 25°57 27°02 24°87 
heel LPOs 13°68 13°91 14°49 13°68 __ 
creases up tothe fifth day, the increase becoming, however, very 
slow as that limit is approached. It is also found that the in- 
gredients offering the greatest resistance to this action are the 
same as those whose amounts were sensibly affected by the 
strength of acid, viz., Silica, potash and alumina.* 
In regard to lime and magnesia, one day's digestion not being 
sufficient for full extraction, it is evident that they do not exist 
in the soil as carbonates or hydric oxides only, as has been sup- 
posed ; but also as silicates. 
_ A comparison of the results of the five and ten day diges- 
tions shows that the solvent action of the acid has substantially 
ceased, there being no further increase of the amount of dis- 
Solved matter. 
So far, therefore, as the time of digestion is concerned, the 
analyses of the Mississippi Survey are strictly comparable with 
those of Arkansas and entucky soils, made by Dr. Peter. 
Art. V.—On a new form of Cathetometer ; by WILLIAM 
GRUNOW. 
_ THE cathetometer consists essentially of a graduated vertical 
Tod, on which slides a block supporting a leveling telescope. 
The block is commonly divided into two distinct pieces, both 
* There is tk | in the four days’ digestion, owing to 
“oa a denciey sepaianiee nga Br canisey ia eaaracpoalinly in- 
