TRANSACTIONS OF SECTION B. 321 



length of 15-inch pipes that I have used has been only 15 feet, and in this short 

 length a plentiful stream of water can he changed into acid, 24° Twaddel, when 

 the vitriol has been freshly run on the salt. Of course where the charge has boiled 

 down this cannot be maintained with such a short length of tube, hence, up to the 

 present, strong acid has been delivered down the tube by a pump 1 introduced to 

 the trade about two years ago. Ultimately, I trust, no acid pump will be needed 

 in connection with the condenser, but the gas cooled and the acid made from 

 water alone. 



A vertical range of 12 inch pipes filled with coke and supplied with water is 

 provided to make away with the remains of the gas ; this may be all put under 

 pressure by narrowing the exit. There is reason to believe that a very short range 

 will eventually be required here, even if one be needed at all. 



The large powers of cooling and acid making shown by 15 feet of piping 

 chequered with tiles, show that further development may be expected in this 

 direction. If 15 feet can do so much, what of 30 or 50 feet ? In this way I hope 

 to dispense with acid pumping entirely. 



The highest test taken at the exit pipe showed an escape of l - 2 grains per 

 cubic foot, and the lowest test - 09 grain per cubic foot. This on a 12 inch 

 pipe, with a speed too slow to be found in the usual fashion, would yield merely 

 a fractional percentage on the salt used, or a figure in the third place of decimals 

 if reckoned on a cubic foot taken from a moderate sized chimney with 6 or 8 

 feet of speed a second. These satisfactory results obtained at the outset are most 

 encouraging, and lead me to hope that ultimately the very smell of the acid vapour 

 may be quenched. 



If this method prove capable of making vitriol, it will effect changes of an 

 importance difficult to estimate. 



The old plan stands aside, as it were, provides long lanes of piping in which 

 the gas may spread its giant bulk and wander on, until weary with gradual 

 cold, it slowly submits to the liquid form. The new plan stands directly in front 

 of it, quenches its fire ere it has gone six yards, draws it swiftly on, and crushes it 

 between cool surfaces of liquor until its power to harm has passed away. 



WEDNESDAY, AUGUST 27, 1879. 



The following Papers were read : — 



1. Notes on a Sample of Fuller's Earth, found in a Fullouica recently 

 excavated at Pompeii. By William Thomson, F.R.S.E. 



In visiting the ancient city of Pompeii in April last, I observed in one of the 

 Fullomca establishments a large square tank set in the ground, filled with a white, 

 soft substance, which was soapy to the touch, and which was pointed out to us as 

 the soap of the ancient inhabitants. I took a sample of the substance with a view 

 of making a chemical examination of it. 



( This substance is named by the Italians ' Terra Fullouica,' and besides beinur 

 found in the dyers' and washers' quarter of the city, it has been discovered fre- 

 quently in the ordinary houses which have been excavated. 



Among the literature of chemistry I searched for but failed to find any 

 mention of this Fuller's earth or its composition, but through the kindness of 

 Signor Felice Niccoline, Director of the National Museum of Naples, I obtained a 

 pamphlet written by Professor de Luca, entitled, ' Chemical Researches on " Terra 

 Fullonica," found in Pompeii, April 13, 1878.' 



In this he gives the general chemical peculiarities of the clay, such as its being 



1879. t 



