stationary knife, fixed on the table over which the paper travels.

Water-marked papers have to be cut very accurately at equal distances between the water-marks; cutters with special clamps gripping the paper and bringing a certain length of paper forward to the cutting knives each time, are used for this purpose.

The "Guillotine" cutter is one type of cutter, which is used for trimming sheets or dividing large sheets into smaller ones. The essential part of this cutter consists of a heavy knife which, in its diagonal downward movement, cuts through the pile of sheets firmly pressed together on the cutting table.

The importance of testing papers systematically has been recognised in various countries, but especially in Germany. The pioneer in this branch of testing was the splendidly equipped testing Institute at Charlottenburg: this establishment includes a department devoted entirely to paper testing, with the development of which the name of its Director, Prof. Herzberg, is intimately connected. The great value of paper testing does not consist alone in ascertaining the quality and the properties of a given sample; the result of systematic tests cannot fail to be invaluable to the papermaker, because, by their consideration, irregularities will be exposed and remedies will suggest themselves.

The real object of the testing institute was not at first recognised by the German papermakers. The idea prevailed that such conditions would be exacted as would only subject the manufacturer to further heavy burdens. Experience has proved, however, that the testing institute is a true and valuable friend to the paper-maker. The preface of Herzberg's second edition of "Paper Testing" (Papier Prüfung), contains a letter addressed by the German Paper-makers' Association, in 1900, to the Ministry of Education, which expresses the prevailing opinion so clearly, that I think it will be of interest to give a translation of it here:

"The work of the Charlottenburg Institute since its foundation, has been followed by the German paper-makers with the greatest interest. Although at first it was not considered always convenient to have the department of paper testing, which was -established simultaneously with the institute, as a severe judge, no attempt has been made to conceal that paper testing has been a powerful factor in contributing to the growth, the importance, and the prosperity of the industry, and in establishing its fame as against foreign countries."

To bring paper testing to the position which it should occupy in order to be of real value to the industry, it must be conducted on lines similar to those adopted by the Prussian authorities.

Proper paper standards should be established; these have proved a boon, not only to the buyer, but also to the paper-maker. The results of all the tests, as well as of investigations into the composition of foreign papers which compete against the home industry in our markets, ought to be published periodically and thus placed at the disposal of our manufacturers.

In many instances, conclusions may be deduced from the results of these tests which might prove to be of value to the paper-maker. Very often it will be found of importance to ascertain microscopically the kind or kinds of fibres from which a paper has been made. For the microscopical examination of papers are required a good microscope and various chemical reagents by means of which the fibres are coloured. To prepare a paper for examination, it is necessary to disintegrate it by boiling small pieces, taken from various parts of the sheet, for ten to fifteen minutes in a weak solution of caustic soda (about 1 per cent.); during this operation papers containing mechanical wood are coloured yellow. The boiled paper is now placed on a fine sieve, washed free from soda, and transferred to a bottle containing garnets. After a short shaking with water, the pulp is drained and is then ready for the preparation of the slides.

The chemical reagents used for facilitating the investigation are potassium iodide iodine solution, and zinc chloride iodine solution. On placing a few drops of the former on a small quantity of the pulp placed on a slide, the principal fibres show the following colouring:-Linen, cotton and hemp-light to dark brown. Straw and jute cellulose-grey. Wood cellulose and esparto-partly grey, partly brown. Manila hemp-partly grey, partly brown, partly yellowish brown. Wood pulp (mechanical) and raw jute-partly yellow, partly yellowish brown.

Zinc chloride solution gives the following reactions :-Cotton, linen, and hemp-claret red. Wood, straw, esparto, and jute cellulosepartly blue, partly reddish and blueish violet. Manila hemp-blue, blueish violet, dull yellow, and greenish yellow. Wood pulp and raw jute-lemon to dark yellow.

Before applying zinc chloride solution, the pulp must be freed from water by squeezing it

on a porous plate. The fibres have to be separated with a pair of platinum preparing needles and then covered with a thin cover glass.

Considerable experience is required in working with the microscope and a careful study of the structural characteristics of the different fibres is essential.

Cotton fibres appear under the microscope as flat ribbons, usually twisted upon themselves. The flax fibre appears round and fairly regular, and shows a distinctly visible narrow central canal. Numerous dark lines run cross ways, and are due to pores in the fibres. The so-called linen bulbs are very characteristic widenings of the fibre. Hemp fibres, as present in papers, cannot be distinguished with certainty from flax fibres. Mechanical wood shows a ragged torn appearance and its structure is not a fibrous one. The pitted vessels or pores, which appear in the shape of two concentric rings, are very plainly visible. Cross markings on many of the wood cells may also be frequently noticed. The bast fibres of jute are distinguished by a distinctly visible canal, the width of which varies considerably. In some places it is completely obliterated, and appears as a single line.

Wood cellulose fibres are usually flat, often twisted and not unlike cotton. In many instances the characteristic rings as seen in the mechanical wood are plainly visible in the cellulose.

Straw fibres are round and smooth and accompanied by numerous cuticular cells some of which are very wide and flat whilst others are peculiarly marked and serrated. The spiral shaped cells carry a ring at each end and although the cells are mostly torn, the rings may be always found in straw papers.

Esparto fibres and cells are very similar in appearance to the straw fibres and cells. The characteristic small pear-shaped hairs or cells, which are always found in esparto papers, afford, however, a ready means of distinguishing esparto from straw.

To ascertain the respective quantities of fibres present in a paper it is necessary to compare the microscopic preparation with fibre mixtures of known composition. Very -considerable experience is, however, required to obtain results possessing a high degree of accuracy.

The thickness of a paper may be ascertained by using one of the ordinary micrometer arrangements, such as those of Schopper, Rhese and others by means of which measure

Before proceeding with the testing of machine-made papers, the machine way and the cross way of the paper respectively must be ascertained. Both methods used are based on the assumption that the fibres in the machine way are more closely felted than in the cross way.

Valuable conclusions may be drawn from the results of determination of the resistance which a paper offers to tearing. Papers which have to be tested should be kept for some time in a room the air in which contains a known percentage of moisture, as the results are considerably influenced by atmospheric conditions. Strips, 15 mm. in width, are then cut length ways and cross ways from different sheets.

The chief tearing machines used in paper tearing are those of Schopper, Hartig-ReuschLeuner, and Wendler. In Schopper's type, the strip of paper, 180 mm. in length, is suspended vertically between two clips, and by means of a simple hydraulic device, the load is gradually increased, until the strip breaks. The breaking load and the elongation are indicated on two scales.

In the Hartig - Reusch - Leuner type of machine, tension is put on the strip by means of a steel spring, and the breaking load as well as the elongation are given in the form of a curve, the apparatus containing an automatic registering device.

The Wendler tearing machine, in which the load is increased by means of a spring, differs from the last named in that the breaking load and the elongation are indicated on separate scales.

The tensile strength of papers may be very conveniently expressed by giving the length of a strip of paper which, if fastened at one end and allowed to hang free, would break by its own weight. The width of the strip is immaterial.

The resistance which a paper offers to crushing, rubbing, and folding, may be considered as next in importance to its resistance to tearing. Although a paper may be quite good so far as tearing is concerned, its resistance to rubbing, &c., may not necessarily be so satisfactory. Tests of this kind have until lately been exclusively made by hand, a method the results of which obviously depend much upon the individual by whom the tests are made. Schopper has constructed a special machine for this purpose which has been found to give reliable

The ink and water resisting qualities of papers are tested by means of solutions of ferric chloride and pure tannic acid, which, when mixed, produce a black colour lake. The ferric chloride solution is applied to one side, the tannic acid to the other side of the paper. Penetration and consequent contact of the two solutions will be impossible if the paper is hard sized, whilst the grey or black discolouration will rapidly appear on soft sized papers.

The

facture of the simpler coal tar products, the results of laboratory research can be immediately applied in the works itself. mechanical appliances used on the large scale are, as a rule, of a quite simple character and the carrying out of the preparations in the works is not complicated by the necessary use of highly intricate machinery.

In the cases of other industries of a chemical character, such as bleaching, dyeing, calico printing and finishing, the application of any