462 Cconomy of Fuel.—Boiling Springs of Java. 
well defined sections which our coasts frequently preserit, yet 
the progress of the scierce has been hitherto greatly impeded by 
the variety of names given to the same species of rock, and from 
the want of cliaracteristic and well arranged specimens. Many 
persons who have felt the truth of these remarks, and have read 
Mr. Bakewell’s “ Introduction to Geology,” or attended his lec- 
tures, have repeatedly requested him to supply them with such 
rock specimens and descriptions as might enable them to pursue 
the study. He has therefore been induced to devote a consider- 
able time to visit distant parts of our islands, purposely to select 
a series of instructive specimens in order to form geological col- 
lections, showing the principal rocks in their most characteristic 
form, and also their gradations and transitions into each other. 
These collections are accompanied with a descriptive catalogue 
by Mr. Bakewell, which, besides containing the names of each 
rock as given by the English, French, and German geologists, 
and marking their localities, will also notice peculiarities that 
serve to elucidate any striking fact in the science, or havea re- 
ference to prevailing theories. 
Collections varying in size and value may be had by applying 
to Mr. Bakewell at his house, 13, Tavistock-street, Bedford- 
square. 
(ECONOMY OF FUEL. 
The gentleman who sent us the article inserted in our last: 
under this head, writes us, that he had then only speculated on 
the possibility of the balls which he recommended answering the 
intended purpose ; but having since tried them, he finds that, with 
the proportions therein stated, they resist combustion. 
BOHLING- SPRINGS OF JAVA. 
The Penang Gazette of Feb. 10, 1816, contains the following’ 
article on the volcanic springs of boiling mud in Java: 
‘* Having reeeived an extraordinary account of a natural phe- 
nomenon in the plains of Grobogna, fifty paals north-east of 
Solo; a party set off from Solo, the 25th Sept. 1814, to exa- 
mine it.—On approaching the dass or village of Kuhoo, they 
saw between two topes of trees a plain, an appearance like the 
surf breaking over rocks with a strong spray falling to leeward. 
Alighting, they went to the ‘ Bluddugs,’ as the Javanese call 
them, ‘They are situated in the village of Kuhoo, and by Euro- 
peans are called by that name. We found them:to be on an 
elevated plain of mud about two miles in ¢ircumference, in the’ 
centre of which, immense bodies of soft mud were thrown up to 
the height of ten to fifteen feet in the form of large bubbles, 
which, bursting, emitted great volumes of dense white smoke. 
These large bubbles, of which there were two, continued throw- 
ing 
