perforated zinc may be protected by a varnish made of one part (by measure) of coal tar, dissolved in two parts of mineral naptha (kerosene will answer the purpose). The varnish must be sparingly applied, and by means of a brush with stiff bristles; a little care in the application, aided, while the varnish is still liquid, by a rapid swing of the tray or filter through the air, will prevent closure of any of the perforations. Other paints or varnishes may be tried and may bo found preferable to the above. I would suggest a trial of a varnish made of

equal measures of coal tar and mineral naptha, for application in the place of the zinc-white paint. The filter, after it has been painted and varnished, must be exposed in the sun till all smell has gone off.

If,

after

painting

and

varnishing,

the trays don't

fit,

their

size should be altered.

This filter has and

its

now

universal

been

finally approved by Government,

adoption

Dr. Macnamara has had the

conveyed

to him for the

bestowed

on

appliance.

THE MACNAMARA FILTEIl. It is found sometimes that the zinc which enters into the

construction of this Alter undergoes corrosion. consists in the

application

of two

or

three

The

remedy

coatings

of zinc-

paint applied within and without to all parts of the filter, except tlie perforated zinc and earthen-ware plate. The following are Dr. Maenamara's directions : The perforated diaphragm plate can bo unsoldered and temporarily removed to allow of the upper compartment being painted. The white

?

the

care

construction

with

British

troops

ordered.

thanks of Government

hearty and ingenuity which he lias of so important a sanitary