Vegetable oils are unfit for the locks of guns. Castor oil will gum up and become filthy in the extreme. Olive oil or “sweet oil” has very often been agitated, with common salt, nitric ether, sulphuric acid or hydrochloric acid to keep it from becoming rancid. Application of such oil, in addition to its bad lubricating quality, will rust and spoil work where applied. If desired to clarify oil, put in a bottle, say a quart of oil, and add about half a pound of fine lead shavings. In a short time the impurities will collect on the lead, when the clarified portion may be poured off. Let the bottle stand in the sun for two or three weeks during the process, and then filter through fine white blotting-paper. If some portion be found to congeal by cold, separate the clear portion from the other, reserving the uncongealed for use during exposure of the gun to cold weather. _Gunsmith’s Glue._—Dissolve four ounces of good glue in sixteen ounces of strong acetic acid by exposure to gentle heat. This is not exactly a liquid glue preparation—it is only semi-liquid. It may be kept for any length of time desired, and, when wanted for use, a slight warming up is all the preparation necessary. The gunsmith finds it not only very convenient, in case he should have occasion to use glue about his woodwork, but also very good. CHAPTER XXXV. ON JUDGING THE QUALITY OF GUNS. _The Muzzle-Loading Shot-Gun._—In the days when the gun of this character was at its zenith, its quality could be approximately decided upon by a glance at the manufacturer’s brand which it bore, but at present that rule cannot be so safely trusted. Many of the houses which built for themselves a fine reputation by the manufacture of fine guns of the muzzle-loading order, have either ceased to exist, or have gone exclusively into the manufacture of breech-loaders, consequently the old brands, though they may still be met with, are not reliable. In truth they are more often dangerous signs than otherwise, in consequence of the fact that unscrupulous manufacturers not unfrequently apply them surreptitiously as an agent to aid in working off their bogus goods. It is, therefore, best to give brands but little consideration in judging the quality of new muzzle-loaders, trusting mainly on personal knowledge as to what a good gun should be, backed up by thorough test in all cases where such a thing is necessary.