ON PLANTING TREES 



141 



little iron, and generally a little silica 

 or alumina. 



Gravimeter, the name given by M. 

 Guyton lo an instrument for measuring 

 specific gravities; he adopts this name 

 rather than either areometer or hydro- 

 meter, because these latter terms are 

 grounded upon the supposition that a 

 fluid is ahvavs the thing; weighed; where- 

 as with regard to solids, the liquid is the 

 known term of comparison to which the 

 unknown weight is referred. 



Gravity, in physiology, the natural 

 tendency of bodies towards the centre. 



Gravity {specific) is the relative, 

 comparative or apparent gravity in any 

 body, in respect of that of an equal bulk 

 or magnitude of another body. In estimat- 

 ing the specific gravity of different sub- 

 stances,distilled water ata given tempera- 

 ture is fixed on as a standard. Thus 1000 

 ounces of water (Avoirdupoise) = 62A lbs. 

 in a cubic foot is said to be=1000 ; gold 

 = 19,258 ; gold hammered = 19,362; 

 platina = 19,500; platina rolled = 22',06 9; 

 cast iron = 7207; bar iron either hardened 

 or not=77SS. 



Graustein, in mineralogy, is a rock 



composed of small grains of felspar and 



I hornblende, which graduate into each 



I other, and form a mass almost homogenous, 



of an ash-gray color. It contains olivine 



and augite. 



Gregorian year. The greatest part 

 of Europe have long used the Gregorian 

 style, but Great Britain retained the 

 Julian, till the year 1752. The Gregorian 

 is found not to be exactly conformable to 

 the true solar year, but varies from it one 

 hour and twenty minutes in each 400 

 years. 



Gum, a thick transparent, tasteless fluid, 

 which sometimes exudes from certain 

 species of trees. Gum is dissolved by 

 water; the solution is known by the name 

 of mucilage. It is insoluble in alcohol, 

 in which respect it differs from resin; that 

 substance being soluble in alcohol, but in- 

 soluble in water. 



Gunter's chain, the chain in common 

 use for measuring land according to the 

 true or statute measure, so called from 

 M. Gunter, the reputed inventor. 



The length of the chain is sixty-six 

 feet, or twenty-two yards, or four poles 



of five yards and a half each, and it is 

 divided into one hundred links of 7.92 

 inches each. 



This chain is the most convenient of 

 any thing for measuring land, because 

 the contents thence computed are so 

 easily turned into acres, the reason of 

 which is that an acre cf land is just equal 

 to ten square chains, or ten chains in 

 length and one in breadth, or equal to 

 100,000 square links. Hence the dimen- 

 sions being taken in chains, and multi- 

 plied together, it gives the content in 

 square chains, which therefore being 

 divided by 10, or a figure cut off for 

 decimals, brings the content to acres after 

 which the decimals are reduced to roods, 

 and perches by multiplying by 4 and 40. 

 But the better way is to set the dimen- 

 sions down in links as integers, consider- 

 ing each chain as one hundred links; 

 then, having multiplied the dimensions 

 together, producing square links, divide 

 these by 100,000, that is, cut off five 

 places for decimals, the rest are acres, 

 and the decimals are reduced to roods 

 and perches as before. 



Example. Suppose in measuring a 

 rectangular piece of ground, its length be 

 795 links, and its breadth 480 links — 

 795 

 480 



P. 10,560 



So the content is 3 acres, 3 roods, and 

 10 perches. 



Gypsum {sulphate of lime,) what 

 formerly was called gypsum, or selanite, 

 is now known to be sulphate of lime. 

 It is also distinguished by the name of 

 plaister stone, &c. 



ON PLANTING TREES. 



It is recommended that in digging each 

 hole for receiving the tree it be large 

 enough to receive the roots freely, and 



