MAN AND NATURE. 279 



many of our readers to learn that gold has been found 

 in more than thirty counties of Great Britain and 

 Ireland ; and that by improved metallurgical processes 

 more than 600,000 ounces of silver are annually 

 obtained from the working of our numerous lead- 



mines. 1 



We must speak but cursorily, and in round num- 

 bers, of the economical value of our greater mines. 

 The official return of their total value, as derived from 

 those of every kind in working last year, gives no less 

 a sum than 36,000,000^. a cogent proof, drawn from 

 a single small island, of the mastery Man has obtained 

 over the mineral world that lies below his feet. Coal, 

 that astonishing product of an ancient vegetable crea- 

 tion, comes at the head of the estimate. From an area 

 of about 6,000 square miles of coal-fields in Great 

 Britain, and from mines not fewer than 3,000 in num- 

 ber, we at this time draw nearly 90 millions of tons 

 annually, for our own uses and those of the world at 

 large a consumption increasing every year, as men 

 multiply, and steam and other appliances of heat be- 

 come more necessary to do their service on land and 

 sea. The question has of late been often and urgently 

 asked, how long can our English coal-fields suffice for 

 this vast and augmenting drain upon them ? Calcula- 

 tion has been actively applied to answer it, but not 

 quite satisfactorily, inasmuch as the estimates have 

 varied from 400 or 500 to nearly 1,000 years. 2 We 



1 The quartz lodes now worked for gold near Dolgelly, in Wales, 

 have produced in some years as much as 5,000 oz. of this metal. Certain 

 veins here have yielded 12 or 14 oz. from a ton of ore. 



2 We may refer here to a valuable memoir by Mr. Edward Hull on 



