411 
Isinglass- 
putrefaction, the sounds are cut out, washed from their 
slimes and salted for use. In cutting out the sounds the 
intercostal parts are left behind, which are much the best ; 
the Iceland fishermen are so sensible of this, that they 
beat the bone upon a block with a thick stick, till the 
pockets, as they term them, come out easily, and thus 
preserve the sound entire. If the sounds have been cured 
with salt, that must be dissolved by steeping them in 
water before they are prepared for isinglass ; the fresh 
sound must then be laid upon a block of wood whose 
surface is a little elliptical, to the end of which a small 
hair brush is nailed, and with a saw»knife the membranes 
on each side of the sound must be scraped off. The 
knife is rubbed upon the brush occasionally to clear its 
teeth ; the pockets are cut open with scissars and perfect- 
ly cleansed of the mucous matter with a coarse cloth ; 
the sounds are afterwards washed a few minutes in lime- 
water, in order to absorb their oily principle, and lastly 
in clear water. They are then laid upon nets to dry in 
the air, but if intended to resemble the foreign isinglass, 
the sounds of cod will only admit that called book ; but 
those of ling of both shapes. The thicker the sounds 
are, the better the isinglass, colour excepted ; but that is 
immaterial to the brewer, who is its chief consumer. 
This isinglass resolves into fining, like the other sorts, in 
subacid liquors, as stale beer, cyder, old hock, &c. and 
in equal quantities produces similar effects upon turbid 
liquors, except that it falls speedier and closer to the bot^. 
tom of the vessel, as may be demonstrated in tall cylin- 
drical glasses ; but foreign isinglass retains the consisten 
cy of fining preferably in warm weather, owing to the 
greater tenacity of native mucilage. Vegetable acids are. 
in every respect, best adapted to fining ; the mineral acids 
are too corrosive, and even insalubrious in common he- 
