It has been shown that after a time, given suitable conditions involving the presence of moisture, moulds may appear on sheets which were apparently fully smoke-cured, and that under the same conditions other and older samples were unaffected. It is argued that the latter sheets had evidently been smoked more efficiently than the others. Hence it is fair to assume that, except under very special conditions, which do not apply to the ordinary procedure in the shipping, storage, and sale of rubber, moulds will not develop upon sheets which have been properly smoked. The term "properly smoked" signifies efficient smoking for all practical purposes under ordinary procedure, and implies or includes all the advantageous factors which have been discussed or alluded to in preceding paragraphs. Without discussing in wearisome detail conditions which may give rise to the incidence of mildew on properly smoked rubber, it may be pointed out that the following are favourable to the growth of moulds: (_a_) Storing sheets in a damp place before packing. (_b_) Packing sheets in wooden cases which are not thoroughly dry. (_c_) Piling up cases of rubber in a badly ventilated store-room. (_d_) Placing the cases on a cement floor. (_e_) Wetting of cases by sea-water or by rain during transport, etc. BLACK STREAKS, SPOTS OR PATCHES.--The origin of these is not difficult to trace. They are caused by drippings from the roof, and contain condensation products from smoke plus moisture. The ventilation of the roof-ridge should receive attention, and if the trouble persists it will be necessary to place some absorbent screen below the sloping roof. Sackcloth is sometimes used, but leads to a worse state of affairs unless changed frequently. In most modern smoke-houses having an iron roof there is an inner lining of soft timber. There scarcely seems a necessity to discuss the case in which an iron roof has become perforated by the action of smoke. The remedy is too obvious to describe. WHITISH OR GREY STREAKS.--This is a very uncommon defect, and is generally to be traced to a building in which fairly new galvanised sheets have been employed. The zinc surface becomes oxidised, and the whitish powder which is formed "flakes," or is carried away by drops of moisture condensing on the surface of the iron sheets. RUST.--Sometimes if a sheet is stretched forcibly and allowed to retract quickly, the hitherto clear surface will be seen to be marred by a "rusty" deposit. The rubber is then described as "stretching rusty," and its value is depreciated.