of distilled tar, and every large factory uses it at present.  The roofing paper prepared with distilled tar is perhaps most suitably called asphaltum paper, as this has been used in its manufacture.  It possesses properties superior to the ordinary tar paper, one of which is that immediately after its manufacture, as soon as cold, it is dry and ready for shipment; nor does it require to be kept in store for a length of time, and it has also a good, firm body, being as flexible and tough as leather.  It is very durable upon the roof, and remains flexible for a long time.  It is true that asphaltum papers will always in a fresh state contain a small percentage of volatile ingredients, which after a while make it hard and friable upon the roof; but, by reason of its greater percentage of resinous components, it will always preserve a superior degree of durability and become far less porous.  One hundred parts by weight absorb 140 or 150 parts by weight of coal tar.  A factory which distilled a good standard tar for roofing paper recovered, besides benzole and naphtha, also about ten per cent. of creosote oil, used for one hundred parts raw paper, 176.4 partially distilled tar.  Experiments on a larger as well as a smaller scale reduced this quantity to an average of 141.5 parts for one hundred parts raw paper.  The weight of sanded paper is very variable, as it depends altogether upon the size of the sand grains.  It may be stated generally that the weight of the sand is as large as that of the tarred paper.

The kinds of roofing paper saturated with other additions besides coal tar form a separate class, in order to neutralize the defects inherent in coal tar.  These additions were originally for the purpose of thickening the paper and making it stiffer and drier.  The most ordinary and cheapest thickener was the coal pitch.  Although the resinous substances are increased thereby, still the light tar oils remain to evaporate, and the paper prepared with such a substance readily becomes hard and brittle.  A better addition is the natural asphaltum, because it resists better the destroying influence of the decomposition process, and also, to a certain degree, protects the coal tar in which it is dissolved.  The addition of natural asphaltum doubtless caused the name of “asphaltum roofing paper.”  Resin, sulphur, wood tar and other substances were also used as additions; each manufacturer kept his method secret, however, and simply pointed out by high sounding title in what manner his paper was composed.  In most cases, however, this appellation was applied to the ordinary tar paper; the impregnating substance was mixed only with coal pitch, or else a roofing paper saturated with distilled tar.  The costly additions, by the use of which a high grade of roofing paper can doubtless be produced, largely increased its price, and on account of the constant fall of prices of the article, its use became rather one of those things “more honored in the breach than in the observance,”