Times of March 17,1864, by Peter Spence of the Manchester Alum Works, who says - "For every boiler, 2 lb. of soda ash (an article easily procured at 1 1 1/4d. per lb.) is every day given to the stoker; this he dissolves in a bucketful of cold water, and puts the solution into the water supply for the boilers; this he does as part of his imperative daily duties, and the consequence is that now not the slightest corrosive action takes place, an additional advantage being that no crust is ever formed in my boiler, all the lime salt that forms these crusts being also destroyed by the alkaline solution."

No attempt should be made to soften water or employ anti-incrustators without first making a searching inquiry as to the nature of the waters available and the scale they may form. No special law can be laid down for the softening of water or the use of anti-incrustators - the cause of the disease must first be learned, and then the remedy may be safe and sure. To limit the materials used, by laying down a hard and fast law, would be to cause injury and loss to the steam user. The best results are obtained by the employment of a man of skill, and the rigid working out of his suggestions.

The discussion which followed Macadam's paper elicited the following remarks. Deposits from waters containing both carbonate and sulphate of lime vary considerably, from a tough fibrous deposit very difficult to remove, to a light friable deposit that can almost be blown out of the boiler; but nothing appears yet to be known about the proportions of carbonate and sulphate which are most favourable. Some years ago Ekin went into the question of water supply for the Somerset and Dorset Railway, as it was found that, with their steep gradient over the Mendips, the water they took from the Avon furred the boilers so quickly as to occasion great loss. He selected a different watering station with the best results, but, chemically speaking, there was very little difference between the objectionable and the good water, the permanent and total hardness bring nearly the same in both. In this case the hard deposit from the Avon water may have been caused, in part, by the large quantity of sewage the river contained at the point from which the boiler supply was taken.

B. E. R. Newlands observed that he was able to effect the removal of matters likely to cause incrustation, before the entry of the water into the boiler, with many thousands of gallons of river water a day, at the cost of about Id, per 1000 gal., by an adaptation of the Porter-Clarke process. While there are undeniable advantages in water heaters, yet there was usually not even partially effective deposition of the separated matters before entering the boiler, without the use of a specially-constructed filter press. The same remark applies to the results of the use oftripsa." The lime phosphate might be utilized if the boiler were regularly blown out, and no doubt a suitable filter-press could easily be constructed to meet the peculiarities of the case. The purification of water for steam-raising purposes is much to be preferred to the employment of anti-incrustators placed inside the boiler; but of course, such processes cannot always be used, from want of space, or on ships. Whilst the Porter-Clarke process only removes from solution the calcic carbonate and magnesic'carbonate from water with any small proportion of iron salt present, yet each deposit, on falling down, encloses the suspended matters, whether of organic or mineral origin, and thus causes their removal.

A reference to the results of the analyses of the waters from the mechanical heaters, and from the other heated-water supplies-, shows this conclusively. In mechanical heaters, the tubes, doubtless by the constant currents of water, remain clean for a long time, while the sides become coated with a deposit, which should not be removed, as its non-conductivity retains heat. Mechanical heaters, to be of the greatest use, require to have some filtering apparatus attached, to eliminate the precipitated calcium and magnesium carbonates; this would entail a loss of heat, and thus greatly reduce the utility of the heaters. With paraffin lubricants as anti-incrustators, the condensed steam can be used without damaging the plates or fittings, but would not be suited for blowing into water used for dyeing, boiling fibres, etc.

(See also 'Workshop Receipts,' and Spons' ' Dictionary of Engineering.')