In fact, the operator who proceeds with a perfect knowledge of the principles of his art, and of the results of its application, will never ascribe the failure of his process to caprice, but will impute it to the neglect of some indispensable precaution in the application of his principle; and his disappointment will serve as a guide for him to calculate better and improve his preparatory process. Convinced that the effects that flow from his principle are invariable, he knows that every kind of loss and damage can proceed only from an error in the application of his principle. § XI. _New-laid Eggs._ The more fresh the egg is, the longer it withstands the heat of the water-bath. I consequently took eggs the day they had been laid, placed them in a jar, with raspings of bread, to fill up the vacuities, and secure them against breaking when removed to a distance. Having well corked, tied and luted the jars, &c. I placed them in a boiler of a proper size[K] to give them seventy-five degrees of heat.[L] Having taken the water-bath from the fire, I took out the eggs as soon as the water was so cool that I could put my finger in it. I then took out the eggs and kept them six months. At the end of that period I took the eggs out of the jar, put them into cold water which I set on the fire, and heated it to seventy-five degrees: I found them fit to dip a toast of bread into, and as fresh as when I prepared them. As to hard eggs, which are to be cut into slices and fricaseed, I heat the water-bath eighty degrees, and as soon as it begins to boil, I remove the water-bath from the fire. [K] This operation performed on a great scale, that is in a larger boiler, would require too much exactness, as it would be more difficult to command just the due degree of heat in such a boiler than in a small water-bath which may be set on and taken off at pleasure. [L] That is, of _Reamur_, or 200 of _Fahrenheit_, in like manner, the 80 of Reamur, or boiling point mentioned below, is 212 of Fahrenheit. T. § XII. _Milk._ I took twelve _litres_ of milk fresh from the cow; I condensed it in the water-bath and reduced it to two-thirds of its volume, frequently skimming it. Then I strained it through a boulting cloth. When cold I took from it the skim which had risen while it was cooling, and bottled it, with the usual process, and afterwards put it in the water-bath which I let boil for two hours; and at the end of several months, I perceived that the cream had separated itself and was swimming in the bottle in the form of flakes. To obviate this inconvenience, I made a second experiment on a like quantity of milk which I condensed in the water-bath, reducing it to one half, instead of one third, as I had done the former. I then added to the milk, so reduced, the yolks of eight new laid eggs well beaten. Having left the whole thus well mingled half an hour on the fire, I completed the experiment as before. This expedient perfectly succeeded.