^0.9. 



Marl. — Inflammable Gas. 



27S 



ssential and distinctive ingredient in the 

 reensand stratum, it randy exists unasso- 

 iated witii several substances, particularly 

 lay and white siliceous sand. Tliese consti- 

 ite sometimes as much as 50 per cent, of 

 le bed, — influencincr materially its properties 

 3 an agricultural agent." The I'oliowinor 

 ibie exhibits the average composition of seven 

 )ecimens of the greensaiid marl, taken from 

 3 many different parts of the formation in 

 e\v Jersey, some of them widely distant 

 om the others: The ingredients were sepa- 

 ited by mere mechanical means. 



Greensand 75 07 



Clay 2U.i):i 



Quartzose sand 4.00 



must be evident from the above that the 

 jrsey marl must owe its fertilizing powers 



the greensand, as it contains no other 

 aterial of much efficacy. From the results 

 15 analyses of the greensand mineral itself, 

 i own composition appears to be of 



Silica 49.5 



Alumina 7.3 



Protoxide of iron 22.8 



Pot.-ish 11.5 



Water 



7.9 



Li mo, about 0.5 



Magnesia, a trace. 



" Abundant evidence might be adduced to 

 ove that the true fertilizing principle of this 

 nd of marl is not li'me, but potash,'^ but we 

 ink it unnecessary, as a mere inspection of 

 e above table will fully show that it con- 

 ins no other ingredient in sufficient quantity 

 lich is known or suspected to have any fer- 

 izing powers, particularly on the sandy 

 ils of Jersey ; unless an indirect agency, 

 at of neutralizing the acids in the soil, be 

 Iributed to the protoxide of iron. In this 

 rticular we believe it differs from all other 

 bstances known under the general term of 

 irl. 



Another kind is the shell-marl, found ex- 

 isively in the tide-water region of Virginia 

 d some other states. It is made up of small 

 ;sil shells, or their fragments, and of clay 

 d sand. The average proportion of car- 

 nate of lime in 107 specimens, taken from 

 arly as many different localities in Virginia, 

 d analyzed by Prof William B. Rogers, 

 IS 47.4 per cent, nearly.* The shells in 

 IS marl exist in all states from the most 

 tire and perfect fossil to a broken and finely 

 mminuted mass, and from a soft powder to 

 hard concretion, which might properly be 

 •med a tertiary limestone. Its value as a 

 mure frequently depends more on the fa- 

 ity with which the shells fall into very mi- 

 te particles than on the ab.«olute quantity 



' See his Fourth Annual Report of the Geological 

 rvey of Virginia. 



of the carbonate of lime it may contain. It 

 no doubt owes its fertilizing powers mainly 

 to the carbonate of lime contained in its shells; 

 but some varieties of it contain also a small 

 portion of greensand similar to that of New 

 Jersey, as well as a portion of sulphate of 

 lime, or gypsum, which may aid in ils eff^ect, 

 it has produced the most astonishing effects 

 in the tide-water region of Virginia, — work- 

 ing in fact an entire revolution in the appear- 

 ance and product of many farms where it has 

 been liberally applied. 



In the above brief notices the object has 

 been to show the loose and indefinite manner 

 in which the term marl has been applied, 

 both in Europe and this country, in doing 

 which, so far as relates to the latter, that I 

 might not make "confusion worse con- 

 founded" by attempting to describe what I 

 knew nothing about, I have confined myself 

 for the present to such substances only asiiave 

 undergone the investigations of gentlenum 

 eminent for their science and general intelli- 

 gence, and whose descriptions, therefore, (of 

 which the foregoing is an imperfect abstract,) 

 may be relied on with confidence. 



S. Lewis. 



Inflammable Gas* 



The lightness of inflammable gas is well 

 known: when bladders of any size are filled 

 with it, they rise upwards and float in the 

 air. Now it is a most curious fact, ascer- 

 tained by Knight, that the fine dust, by means 

 of which plants are impregnated one from 

 another, is composed of very small globules 

 filled with this gas — in a word, of small air- 

 balloons. These globules thus float from the 

 male plant through the air, and striking 

 against plants of the other sex, are detained 

 by a glutinous substance prepared on purpose 

 to stop them, which no sooner moistens the 

 globules than they explode, and their sub- 

 stance remains; the gas, which enabled them 

 to float, flying oft'. A provision of a very 

 simple kind is also in some cases made to pre- 

 vent the male and female blo.ssoms of the 

 same plant from uniting ; this being found to 

 injiiie the breed of vegetables just as bieeding 

 " in and in" spoils the race of animals. la 

 this case, it is contrived that the dust shall be 

 shed by the male blossom before the fi-male 

 of the same plant is ready to be affected by it; 

 so that the impregnation must be performed 

 by the dust of some other plant, and in this 

 way the breed be crossed. And the h'vity 

 of the gas with which the globules are filled 

 is most essential to the operation, as it con- 

 veys them to great distances — a plantation of 

 yew-trees has been known in this way to im- 

 pregnate another, several hundred yards dis- 

 tant. — Brousham, 



