" 'We advise generally against the inks known simply as writing fluids--those not intended to yield a letter-press copy--because they are universally made, first, with as little solid matter as possible,--i. e. weak; second, with an excess of iron beyond that required to combine with the tannin, so as to develop all the color possible and flow with the greatest freedom. The combined writing and copying fluids, and the copying fluids on the other hand if properly made, may be justly recommended where permanency is the first requisition, particularly the older ones, which should be the most durable of all nut-gall and iron inks, because in them particularly concentration is aimed at, and the iron need not necessarily, and should not, be in excess of that required to combine with the tannin present. A steel pen during use injures, and often greatly, the durability of a writing ink by giving up iron to it. " 'For your purpose, where extreme permanency is the first requisition, I should not advise the use of an ordinary writing fluid. Many manufacturers cannot obtain sufficient fluidity in their writing fluids without making their inks very dilute, and observing a particular method of manufacture which, although providing more attained color for a time, sacrifices the permanent quality of their color in a great measure. I should advise the use of an ink decidedly stronger.' "The addition of water was almost universally condemned, for reasons stated later. As proof that this was not for the mercenary purpose of indirectly advising the use of more ink, some of the manufacturers said the ink should be kept in small- mouthed ink-stands, and when not in use should be as tightly sealed as possible, to prevent evaporation. "In reply to the inquiry as to whether chemicals left in the paper ever obliterated the ink, several of the manufacturers said they knew of such cases, and all were agreed that, if the chlorides used for bleaching the paper were not washed out, they would dangerously affect any ink. The practice of mixing inks was universally condemned. "Permanency against the action of time is the quality sought for in this investigation, and it is claimed that better evidence as to that quality is furnished by the test of time than by any other; and manufacturers have shown or referred to specimens of writing made with their ink many years ago, as proof of its merit in this particular. If there was any surety that the standard of quality was always kept up in all of the oldest inks on the market, it would be safe to accept that test, but this may not be a fact; and, as has been stated, some of the recording officers believe that it is not.