154 Scientific Intelligence. [Aug. 



buoyancy, amounting to 1943 grs. and for the difference of tempera- 

 ture of the water and brass conjointly, the densities being -999955 and 

 •999810, the correction -000145 — -000047 = -000098, or 1-86 grs. 

 leaving + 17'57 grs. for the whole correction of the weight, as reduced 

 to a vacuum at 62°, and making it 19024'40, which, divided by 

 75*2398, the content of the cylinder, affords us 252*851, for the cubic- 

 inch in a vacuum at 62°. 



The sphere was weighed in air at 67°, the barometer standing at 

 29-74<; the correction for buoyancy is here i'4-.-^i 9 •■?+?, or for 

 28673*51 grs. 29*72 : while the temperature of 66° requires, for the 

 difference between the expansion of brass and water, the addition of 

 •00042 — -000126, or -000294 of the whole; that is + 843 grs. mak- 

 ing the whole correction 3815, and the weight in a vacuum 2871T66; 

 which, divided by 113-5264, gives us 252*907, for the cubic inch in a 

 vacuum. 



The mean of these three measures is 252*888, giving for the three 

 errors + -019, — *037, and + *019; and this mean, reduced to the 

 parliamentary standard, makes 252722 grs. for the cubic inch of dis- 

 tilled water at 62°, weighed in a vacuum, or 252*456 in air, under the 

 common circumstances of the atmosphere, when weights of brass arc 

 employed. In a vacuum at the maximum of density, that is at 39°, 

 the weight of a true cubic inch will be 253 grs. and of a cubic deci- 

 metre 15440.* The proposed Imperial Gallon, of 10 pounds, or 70000 

 grs. of water, will contain very nearly 277"3 cubic inches under com- 

 mon circumstances. 



II. Potash from Potatoe Stalks. 



According to some experiments stated to have been made in France, 

 and detailed in the Philosophical Magazine for November, 1817, 

 2000 lb. of potash are obtainable from the stalks of an acre 

 of potatoes. Mr. llice, who tried the experiment in Ireland, found 

 that only 20H lb. could be obtained. "With a view to verify or cor- 

 rect the French statement, Sir John Hay, Bart, at the request of Dr. 

 Macculloch, made a large experiment on his farm near Peebles. 

 Dr. Macculloch states, that the experiment was conducted implicitly, 

 according to the directions given in the narrative of the French experi- 

 ment, from the cutting to the burning of the plant; and the ashes were 

 examined by Dr. Macculloch himself. 



The results of two trials on separate acres were as follow : premising 

 that the Scotch acre is one-seventh larger than the English, and pre- 

 suming that, in the original statement, the measures were reduced to the 

 English acre. The first acre was a rich loamy soil at King's Meadows ; 

 the potatoes were drilled, and produced a good crop. They were cut, 

 as directed, immediately after flowering, left 10 days to dry, and burnt 

 in a pit. The produce was 2'i2 lb. of ashes, and in hxiviation and 

 drying these yielded 55 lb. of impure potash, or mixed salts. 



The second acre was a clayey wet soil, with a retentive bottom ; 

 but the crop, which was also drilled, was considered moderate. Those 

 stems were treated in the same manner; but the burning was more 



* It appears, however, from an official Report, obliginglj communicated to us by l>r. 

 Kelly, that the actual standard chiliogturhmc has beer, found to contain only 13433 

 English ••' 



