freely, until one day a cracked elbow, tar coated, was detected.
Since that time plain, untarred pipe has been specified, and subjected to
the so-called kerosene test, which consists of swabbing out each pipe with
kerosene or oil and then allowing it to stand for a few hours. A moment's
thought will convince any one that when a pipe is asphalted or tar coated
it is very difficult to detect either sand holes or small cracks, and the
difficulty of proper calking is increased, as lead does not cling so well
to the tar as to plain iron.

At present, the kerosene test, so far as the writer is concerned, is a
misnomer, because raw linseed oil is used exclusively as giving more
satisfactory results, and being less troublesome to apply.

I have here a length of the ordinary "heavy 4" commercial soil pipe,
plain, and selected at random. Yesterday noon I had it oiled at my office,
in order to be ready for to-night, and you see, by the chalk marks I have
made, just where the leaks were and their area. I may say here that a
sound pipe of this caliber and standard weight is the exception rather
than the rule, and it was selected for this experiment merely to try and
show the reaction a little better than the heavier pipe might.

Experiments of this nature I have carried along for the past two years,
and I am glad to say that, since I began, the quality of the soil pipe
furnished by the dealers for my work seems appreciably better than at
first. Whether the poorer pipe is still made and sold to other customers I
have no means of knowing; probably it is, however.

A large quantity of the pipe is now being tested at my suggestion by the
Superintendent of Construction of the Johns Hopkins Hospital, at
Baltimore. I have not yet heard the results from him, but doubtless they
will be interesting. A brief summary of the results may be of some
interest.

The different makers of soil pipe generally used by plumbers hereabouts
are:

Mott & Company, Abendroth, Blakslee, Dighton, Phillips & Weeden, and
Bartlett, Hayward & Co.

On 4" extra heavy pipe my results have been as follows:

Percentage passed as good, single hub. 60 per ct. to 70 per ct.
Percentage passed as good, double. 20 per ct. to 80 per ct.
Percentage passed special castings,
including Y's and T's. 60 per ct.

5" pipe extra heavy:

Percentage passed as good, single hub. 25 per ct. to 35 per ct.
Percentage passed as good, double. No record.