MAR 



MAR 



265 



genious writer advises as fol- 

 lows : 



'' Having dried and powdered 

 the nfiarle to be examined, pour 

 upon Huy e;ivcn weight ot it a smaii 

 quantity of water. To this mix- 

 ture, well shaken, add a little of 

 the acid of sea salt, and when the 

 consequent effervescence is over, 

 add a little more. Repeat this 

 addition at proper intervals, till no 

 more effervescence ensues. Then 

 throw the whole, with an equal or 

 greater proportion of water, into a 

 filter of grey paper, whose weight 

 is known. When all the fluid 

 parts have passed through, fill up 

 the filter again and again, witli 

 warm wattir. By this means the 

 dissolved particles of calcareous^ 

 earth, adhering to the residue, or 

 entangled in the pores of the paper, 

 will be washed away, and nothing 

 but what is really unsohible will 

 remain in the filter. This residu- 

 um, with the filter, must be com- 

 pletely dried and weighed. Then 

 the difference betwixt it weight 

 and the original weight of the filter, 

 gives you the weight of unsoluble 

 parts contained in the marie under 

 examination. Th s being known, 

 the proportion of calcareous earth 

 in the same marie is evident. The 

 proportions of clay and sand in it 

 are discovered by subjecting the 

 residuum to a proper elutriation. 

 This operation is very simple, and 

 performed thus- Having weighed 

 the dry residue, mix and shake it 

 well with a suflicient quantity of 

 water. After allowing a little time 

 for the subsidence of the grosser 

 parts, let the water, with the finest 

 particles of clay suspended in it, 

 34 



be gently poured off. When this 

 is done, add more water to the 

 remainder, and after sufficient mix- 

 ture and subsidence, pour off that 

 likewise. In the same mariner 

 repeat the operation, again and 

 again, till the water comes over 

 perfectly pure. The substance 

 which then remains is sand, mixed 

 perhaps with some flakes of talc 5 

 and whatever this substance wants 

 of the weight of the residue em- 

 ployed, is the weight of pure clay 

 carried away by tlie water in the 

 process of elutriation.'* — Georgi' 

 cal Essays. 



If five parts in six prove to be 

 calcareous in a piece of marie, the 

 lime is predominant, and it is fit 

 for the stiffer soils; if two-thirds 

 only be calcareous, and the rest 

 clay, it is fit for a sandy soil, (SiC. 



The calcareous part of marie 

 does not produce so quick an effect 

 as lime, when used as manure ; 

 becaase the latter is burnt, and 

 flakes suddenly. This seems to 

 be the true difference, which is 

 not essential ; because the calca- 

 reous part of marie gradually flakes 

 in the eaith without burning. Like 

 lime, it attracts and imbibes the 

 acids of the earth and air, forming 

 a salt, which dissolves the oils, in- 

 creases the pasture of plants, and 

 prepares the food of plants to enter 

 their roots. 



The quantity of marie to be 

 applied to an acre is about sixty 

 loads. Some sandy soils may bear 

 more of the clay marie ; rich soils 

 need not near so much, of the kind 

 of marie which suits them. 



Marie should be mellowed by 

 the frost of one winter before it is 



