1814.] Scientific Intelligence. 235 



in experiments on the subject, and came at last to this mortifying 

 conclusion, that all the old processes were belter than the new, 

 and that all attempts to shorten the time injured the quality of the 

 leather. 



1 suspect myself that what is called tannin by chemists is not a 

 substance uniformly the same, like sugar or gum; but that various 

 bodies may be applied to the same purpose. Mr. Hatchett's 

 artificial tannin is by far too expensive for the purposes of the 

 tanner. 



I have inserted the letter of my correspondent in hopes that some 

 of my readers, better acquainted with tanning than I can pretend to 

 be, will give a satisfactory answer to his queries. 



VII. Use of Cow Dung in Calico-Printing. 



While lately visiting some calico printing manufactories in 

 Manchester, I was much struck with one of their processes, the 

 use of which has never been explained in a satisfactory manner. 

 After the mordant has been applied to the cloth, it is necessary to 

 pass the cloth through an infusion of cow-dung in water before it 

 be introduced into the dyeing vat. If this be neglected, the colour 

 is always bad, and is apt to spread unequally on the cloth. Nothing 

 else has been found to answer the purpose but cow-dung; though 

 many other things have been tried ; and calico printers are obliged 

 to keep 20 or 30 cows for no other purpose than to furnish dung. 

 We are in want of an explanation of this process. What purpose 

 does it serve ? What peculiar substance does cow-dung contain, 

 that renders it indispensable to calico printers ? 



VIII. New Explosion in a Coal-Mine. 



A violent explosion of fire-damp has recently taken place in Heb- 

 burn Colliery, about half way between Newcastle and South 

 Shields, by which eleven lives were lost. A more particular ac- 

 count of this dismal catastrophe will be given in a future number 

 of the Annals <>) Philosophy. 



' IX. Pblcanii Sand from St. Vincent. 



I am indebted for the following curious communication to Mr. 



ailing, of Catnberwell : — 



During the erupliou of the volcano in the Island of St. Vin- 

 cent, on the l^t of May, 1812, the ashes were carried to an 

 imm< stance, even as far as Barbadoes. A specimen of this 



broughl to England, and subjected to analysis, was found to contain 

 the- following proportions of constituents: — 



Oxide of iron 1 



( alenreou earth 8 



Sand and clay 1)1 



100 



