in about half or three-quarters of an hour; then pour upon it 2-1/2 pints more of the drying oil, and let it boil about an hour longer, stirring it frequently with an iron or wooden spatula.  As the varnish, whilst boiling, and especially when nearly ready, swells very much, care should be taken to remove, in those cases, the pot from the fire, and to replace it when the varnish subsides; otherwise, it will boil over.  Whilst the stuff is boiling, the operator should occasionally examine whether it has boiled enough , which may be known by observing whether, when rubbed between two knives, which are then to be separated from one another, the varnish forms threads between them, as it must then be removed from the fire.  When nearly cool, add about an equal quantity of oil of turpentine.  In using the varnish, the stuff must be stretched, and the varnish applied lukewarm.  In 24 hours it will dry.  As the elastic resin, known by the name of Indian rubber, has been much extolled for a varnish for balloons, the following method of making it, as practiced by M. Blanchard, may not prove unacceptable:  dissolve elastic resin cut small in five times its weight of rectified essential oil of turpentine, by keeping them some days together.  Then pour 1 oz. of this solution in 8 ozs. of drying linseed oil for a few minutes; strain the solution, and use it warm.

544.  To prepare rennet to turn milk

Take out the stomach of a calf as soon as killed, and scour it inside and out with salt; after it is cleared of the curd always found in it, let it drain a few hours, then sew it up with two good handsful of salt in it, or stretch it well salted on a stick, or keep it in the salt wet; and when wanted soak it a little in fresh water, and repeat the same when again required.

545.  To make cheese

Put the milk into a large tub, warming a part till it is of a degree of heat quite equal to new; if too hot the cheese will be tough.  Put in as much rennet as will turn it, and cover it over; let it stand till completely turned, then strike the curd down several times with the skimming-dish, and let it separate, still covering it.  There are two modes of breaking the curd, and there will be a difference in the taste of the cheese according as either is observed:  one is, to gather it with the hands very gently towards the side of the tub, letting the whey pass through the fingers till it is cleared, and ladling it off as it collects; the other is, to get the whey from it by early breaking the curd; the last method deprives it of many of its oily particles, and is therefore less proper.  Put the vat on a ladder over the tub, and fill it with curd by the skimmer; press the curd close with your hand, and add more as it sinks, and it must be finally left two inches above the edge.  Before the vat is filled, the cheese-cloth must be laid at the bottom, and when full, draw smoothly over