310 
Supplement to the “ Tropical A gricnUufist: 
[October r, 1890. 
anhydrous acid — hence the name “ basic ” cinder. 
A blast of air is sent through tlie iron in the con- 
verter, ■which is raised to a very higli temperature 
tor the piirpose of oxidizing jjiirt of the carbon 
and other metallic and non-metallic impurities. 
Among the latter is phosphorus -which is oxidized 
into phosphoric acid. This unites -with the lime 
and forms a kind of phosphate of lime. When 
the blast ceases, the oxidized impurities together 
Tfith the phosx^hate of lime rises as a sciuu to the 
top of the converter, and constitutes -ndiat is 
known as ba.sic or Thomas-slag. The slag is 
tilted into lioxes and left to cool, and for some 
time was cast aside as a refuse material. Many 
attempts were made to extract the plio,sphoric 
aoid, but though some succeeded, it was found that 
the processes could not be -worked at a profit. 
Sometime later it was ground to a fine powder 
and applied as a manure with much advantage. 
The phosphate of lime in basic cinder was found 
lobe not the ordinary tri-basic jihosphate of lime 
found in bone and natural mineral irhosphate*, 
but a tetra-liasic phosphate which contained 2’2i 
instead of 168 parts of lime. This compound 
has an advantage over the normal phosphate to 
the agriculturist, for owing to tlie idiosphate 
being supersaturated with lime, the lime and 
phosphoric acid are in a somewhat feeble state 
of combiiratiou, so that the compound can easily 
be decomposed by the carbonic acid in the soil, 
and by the acid juices in the roots of plants. 
Therefore crops can without difficulty extract the 
phosphoric acid from the manure. The amount 
of pho.sphoric acid will, of course, vary with the 
amount of phosphorus in the pig-irOn, — from 1 4 to 
20 per cent, ecpial to from .30 to 10 per cent 
phosphate of lime. Basic slag must be used in 
the form of an exceedingly fine powder for 
appreciable effect. It has been found suitable for 
leguminous crops, turnips, clover, and grass, 
secondly for cereals ; and is well adapted for 
application to marshy land, stiff clays, and wet 
land generally, owing to the caustic lime which 
it supplies. It should be well incorporated -with 
the soil and applied early for effect. No harm 
is said to result even when a]iplied in large 
quantities, but 4 to 10 cwt. per acre, according 
to circumstances, is a fair dose. There is an 
abundant supply of the substance, which is a valu- 
able manure with a future in store for it if it could 
be purchased for about K22 — E25 ]ier ton grounc, 
to ail exceedingly fine powder. It should have 
a guarantee both of fineness and ])orccntage of 
phosphate. 
CRUDE THEORIES REGARDINO THE 
ORIGIN OF CERTAIN PLANTS. III. 
By W. a. Dk Silva. 
My subject in this pajier is the sweel-))otato, 
ISalatas J'MuHh (Sin. Batala). This yam is a 
common food-jjroduct in villages, and ranks ];er- 
haps next to rice and kurrakkan in the, (‘.\tent to 
which it is eaten. The jioorer inhabitants of the 
rural disliicts li ve on not hiiig but thi.s at times, 
and truly tlmy need have no cause- of couqdaiiit 
against the force of circumst anc.i's. The oi-igiual 
home of the jdant is sujqiosed to be America, 
whence it was evidently introdiictid at a V(;ry 
early date, a.« apart, from the ]>lant being (|iiite 
naturalized here, the natives look upon it as an 
indigenous product. There is, moreover, no such 
affix as Rata, signifying foreign, which char- 
acterises a comparatively modern importation, 
while the fact of its being a subject of folk-lore is' 
sufficient to prove that it has existed for a very 
long period in the island. 
Our story' starts with a widow and two 
daughters who lived together in comfortable 
circumstances, till the marriage of the two 
latter, one to a man of wealth, the other to a 
husband of moderate means. Bad times coming 
upon the Avidow, she a Aisit to her 
rich daughter, hoping to get help from her, but 
though she arrived faint and hungry, her ungrate- 
ful child offered her no refreshment ; and even Avhen 
a request for food was made, the answer Avas 
that there AA-as nothing in the house to eat. At 
first the ohl woman AA-as inclined to pity her 
daughter who, she thought, must have become 
])oor like her, self, but again she became suspicious 
of her chikhs ingratitude, aiulAvhen the latter left 
the house for a AA-hile, she looked about and discoA'er- 
ed that a pot full of rice had beeir hidden avA-aA'. 
Full Or sorrowat the thoughtof herdaughter’singra- 
titude, she Avept bitterly, Avith the result that some 
of lu-r tears fell into the pot of rice. Then she left, 
and sought her other child avIio receiA'ed her AA’ith 
all hospitality. Tlie ungrateful daughter AA-as 
pleased on, her return to find her mother gone, and 
proceerled to jiartake of her meal alone, Avhen, to 
her a,stoni,shment, she found the rice reeking 
Avith blood. iSuch aa us her punishment for her 
Avant of filial affection. But the strange sequel is 
the important part of this account, for when the 
bloody meal aalas throAvn aAvay, an unknoAAm plant 
sprung up from the place Avhereon it fell, which 
in course of time developed a tuber to which Avas 
giA cn the name Batala, deriA ed from Bata rice, 
and la blood — an unjileasant enough etymology for 
so estimable a food. 
^ 
BUILDING MATERIALS. 
Section- I. Stone. 
By a Factory Apprentice. 
The names of the A-arious sorts of stones are 
deriAed either from the places Avhere they are 
quarried, or from the substances which principally 
eiiter into their composition. The term “FTee- 
stune " is, a.s its name implies, that sort which 
can be Avrought Avith the mallet and chisel 
or cut with the saAv, an operation Avhich cannot 
b(> performeil on granite, AA-hose hardness re- 
quii'cs it to be dres.sad Avith pointed tools of 
different Aveights and sizes. It includes, the two 
great diA'isions of Limestone and Sandstone. 
Hardness, tenacity and compactne.ss are the 
three chief (jualities re(|iiisite for a building 
stone. It is not the hardest stone Avhich has 
got the greatest tenacity or toughness, for lime- 
stone, though much softer, is not so easily broken 
as glass. 
JAbiarly the same causes, Avhich destroy the 
rocks on tlu' surface of the globe, accelerate the 
(lecaij and destruction of stone. Such causes are 
of tAvo kinds, those of decomiiosition, and those 
of di.sintegration. The former effects a chemical 
change in the stone itself, the later a mechanical 
