370 
THE MEDITERRANEAN NATURALIST 
He expatiates at considerable length on the 
quantity of anthracite which is at present available 
and specially refers to the views that were lately 
expressed by the President of the Leigh Coal and 
Navigation Company. 
The President, he tells us contends that gre,at 
quantities of coal are wasted through bad methods 
in preparing it for market These operations re- 
sult in reducing a large proportion of the coal to 
sizes too small for the market, the percentage of 
waste from this source averaging as high as 20 
per cent of the coal hoisted from the collieries, 
This has been somewhat diminished in recent 
years by the utilization of the smaller sizes of 
coal. 
He thinks that this process of rescuing coal from 
the waste heaps is destined to go much further in. 
the more general use of the finer particles of coal. 
He believes that it may not be going too far to 
suppose that improved methods of mining and of 
preparing coal may enable the use of fuel of one- 
half of the coal now remaining, so that it may be 
assumed that there are still 5,960,700,000 tons of 
a n mracite available before the beds will be wholly 
exhausted. 
The present annual consumption af anthracite 
is about 40,000,000 tons, and this consumption has 
been for some years increasing at the rate of 4 per 
cent, per annum. If the limit of annual product is 
placed at 60,000,000 tons, the United States should 
have coal at this average rate for about 100 years 
though this period may be some-what prolonged 
by the diminution of the output as parts of the 
field cease altogether to produce. 
The production of coal in the world in 1891 was 
519,083,731 tons, against a total output in the 
preceding year of 109,416,396 tons. During the last 
twenty years there has been a marked increase in 
the consumption of coal which was, no doubt, the 
author thinks commensurate with increased indus- 
trial activity. 
Thus, comparing the European countries alone, 
the average annual output for the period of 1881 
to 1890 was upward of 62,000,000 tons greater than 
during the previous decade, and that rate of in- 
crease bids fair to be maintained, so that the world’s 
consumption of coal will soon reach well over 
500,000,000 tons. 
In an investigation made by a royal Cornmis 
sioner as to the ascertainable sources of coal in 
Great Britain it was found that not more than 
146,773,000.000 tons were available at depths not 
exceeding 4,000 feet from the surface, a reserve 
which, at the present rate of increase of population 
and of coal consumption, would be practically ex- 
hausted in less than 300 years. Industrial activity 
fs not only multiplying the demands of consump- 
tion, but has a widening are a of use, to which 
the map of the two hemispheres is the only limit. 
Wonderful deposits of coal are being constantly 
discovered in various parts of the United States. 
Within the last few T years a particularly valuable 
field has been discovered in Washington, the ex- 
tent of which is estimated at from 650,000 to 6 r 5, 
000 acres. In Wyoming, too, a new company, of 
which ex-Gov. Camphell of Ohio is one of the 
leading spirit is doing much to develop the valua- 
ble coal fields. The extent of these new fields is so 
great that nobody has yet attempted to follow the 
example of the Royal Commissioner and figure out 
in how many hundreds of years the coal supply of 
North America will be exhausted. 
The slugs of the Maltese Islands. 
BY 
Dr. Alfred Caruana Gatto. 
Slugs have been in all works dealing with the 
Maltese Molluscs either omitted all together as 
by Ponsonby, Benoit and Gulia, or the two 
species mentioned by Mamo in his “Enumeratio 
ordinata molluscorum Gaulo Melitensium” edited 
by Dr. A. A. Caruana, have been simply referred 
to. Alamo mentions in this work the Limax varie- 
gatu&=Jiavus and the L. gagates which includes 
the nigricans. 
Fielden in the Zoologist No. 29. Yol. Ill May 
1879. “The land and freshwater molluscs of the 
Maltese Group” refers to these two species, say- 
ing that the slugs collected by him, not having 
been kept in alcohol, could not be determined. 
Becher in the Journal of Conchology No. 8. Oct. 
3884 declares that he did not care for the Limaces, 
and reproducing the L.Jiavus and the L. gagates 
of Mamo’s list he adds;—- 
