only mechanically mixed with the hydrogen, and is liable, especially in cold weather, to be deposited in the pipes.  This leaves only a very poor, thin gas, mainly hydrogen, which burns with a pale blue flame, as seen in cold spells in winter.  High heats and short charges in the retorts of the manufactory give a purer gas and a larger production.  Gas made at high heat will reach the consumer in any weather very nearly as rich as when it leaves the gas-holder; for, thus made, the hydrogen and carbon are chemically combined, instead of the hydrogen merely bearing a quantity of carbon-vapor mechanically mixed and liable to deposit with every reduction of temperature.  To relieve the atmosphere of the gases and vapors proceeding from combustion is, of course, the purpose of ventilation.  The sulphuric acid gas and ammonia will be largely in combination with the water-vapor, which also proceeds from combustion, so that all will be got rid of together.  The vaporization of libraries to counteract the excessive dryness (or drying, rather) which causes leather bindings to shrink and to break at the joints, would be of doubtful utility, since it might only serve to carry into the porous leather still more of the gases just mentioned.  The action of both sulphuric acid and ammonia is, undoubtedly, to destroy the fibre of leather, so that it crumbles to meal or falls apart in flakes.

“In a very interesting paper read by Professor William R. Nichols of the Massachusetts Institute of Technology before the American Association of Science at its Saratoga meeting in 1879, the results of many analyses of leather bindings were given, showing the presence of the above-named substances in old bindings in many times greater quantity than in new.  Still, their presence did not prove them to be the cause of the decay; and Professor Nichols proposes to ascertain the fact by experiments requiring some years for demonstration.

“In the hope of deciding the question with reasonable certainty at once, I have made careful examinations of the books in the three largest libraries of Boston and Cambridge, each differing from the others in age and atmosphere.  The bindings of the volumes examined bore their own record in dates and ownership, by which the conditions of their atmosphere in respect to gas and (approximately) to heat were made known for periods varying from current time to over two hundred years.  In the Public Library the combined influences of gas, heat and effluvium have wrought upon the leather until many covers were ready to drop to pieces at a touch.  The binding showed no more shrinkage than in the other libraries, but in proportion to the time the books had been upon the shelves the decay of the leather was about the same as in the Athenaeum.  I am informed that many of the most decayed have from time to time been rebound, so that a full comparison cannot be made between this and the others.  In the Athenaeum less gas has been used, and there is very little effluvium,