86 MARL. 



The presence of much argillaceous earth may be 

 judged by drying the marl, after being washed with 

 spirit of salt, when it will harden and form a brick. 



" To determine with still greater precision, the 

 quantity of calcareous earth in marl, let the solution 

 in muriatic acid be filtered and mixed with a solution 

 of carbonate of potash, till no further precipitation 

 appear. Let the sediment subside ; wash it well with 

 water; lay it on a filter, previously weighed, and dry 

 it. The weight of the dry mass will show how much 

 carbonate of lime, the quantity of marl, submitted to 

 experiment, contained. " 



There have been a variety of opinions held at dif- 

 ferent periods of the world, concerning the efficacy 

 of marl as a manure ; for it is certainly of very an- 

 cient date. Lord Bacon defines marl to be the best 

 compost in use; having fatness, and being nutritious 

 to the earth. An ancient author declares, that a 

 piece of land once marled continued fertile eighteen 

 years, while Anderson's statement is thirty years, with- 

 out further improvement. These are no doubt exag- 

 gerations. 



The word marl signifies in its original meaning, 

 marrow, or fatness, from the supposition that it impart- 

 ed fatness to the earth ; though, as has been shown, it 

 acts from binding or opening the pores of the soil, and 

 from attracting moisture from the atmosphere. The 

 lime has also the power of decomposing vegetable 

 and animal substances in the earth. 



