The cylinders revolve in benches or sockets, gene rally of smooth hard brass or bell-metal ; and all these, excepting those of the main cylinder, are so connected with the lateral thawing by which they are supported, as to treader them capable of being shifted upwards or downwards occasionally. This admits of altering the degree of pressure gives by the cylinders, so as to kWh the great variety of fabrics which are necessarily subjected to the operation of the same calender, if employed in genera/ Whom. The ranhen of pressure exerted upon the cloth is sometimes regulated by projecting levers, operating as steelyards. The short end of these being•connect ed with the centres of the cylinders, the pressure is proportional to the weight applied to the longer ex tremity, and its distance from the fulcrum.
This is perhaps the beet and surest mode of tem pering and adjusting the quantum of pressure. The steelyards, however, require mere space than the proprietors are generally willing to allot for their calendere ; and, consequently, the pressure is meet commonly regulated by screws. This, however. subjects everything to the discretion of the operator, and an unskilfhl person often injures the machinery, and even stops its motion by overscrewing the ca lender. At other times, he is apt to set it so open, as to permit the cloth to pass through it without re ceiving nearly the effect which will be derived when the calender is skilfWly adjusted.
In order that the operating effect of the colander may be merely by pressure, it will be obvious that the relative velocity of rotation, communicated tit each cylinder respectively, should be reciprocally m its diameter; for thus each will expose equal super. flees in equal times. And to effect this, it will be equally obvious, that the diameter of the wheels (reckoned to the pitch lines or working parts of the teeth) should be commensurate with those of the cylinders, upon whose axes they are respectively These diameters being respectively 6, 12 and 24 inches, and that of the wheels the same, the perimeters of this latter (avoiding minute ilsedens) will be nearly 18.8, 87.6, and 75.2 inches ; and to deduce from these the requisite number of teeth, it is only necessary to ascertain what strength it will reeky into whirsh they are to be laborites* that, in their utmost) state of expansion from the heat, they may slide finely along, with as little vacant apace as can eddy be allowed, but without exposing them to ibe danger of ocoasiooal phstruction from excess of diameter.
be necessary to allow for each. An epicycloidal tooth, measuring .75 inch thick at the pitch line, will be abundantly strong to undergo any opposition which it may encounter in a well constructed °slen der ; and should this be adopted, the numbers of the wheels will'be Incises, Main cylinders A, 24 diameter, 48 teeth nearly.
Iron cylinders BB, 6 12 Extreme cylinders CC, 12 24 liable to such modification as the engineer may deem it proper to adopt, under• the special circumstances of each case.
When these connections betwixt the cylinders are formed, and a sufficient moving power is applied to the main cylinder A, the whole will revolve with ve locities proportional to their diameters; and as equal surfaces will he ,exposed by all in equal times, pres sure, alone will be applied at the lines of junction, and the calender, will smooth, by compression exclusively, whatever pieces of cloth may be exposed to its ope ration. This pressure, it is also apparent, will take place at the four lines of contact between the cylin ders, and; of course, will be four times applied du . ring the transit of the cloth. Those who attend the calender most be careful that the pieces are fairly extended before insertion, to prevent creasing ; and that they are regularly ;although loosely collected into regular folds after being calendered ; and in this state delivered to those whose business it is to refold and press them into the proper folds, which they are permanently to retain, until they shall come into the possession of the consumer.
The above description of the common calendar supersedes, in a great measure, what it might other wise be necessary to detail respecting that employed for glazing. Both engines are, in fact, nearly the same ; and the same calender may, by a few minutes labour, be altered so as to answer either purpose.
Previously to the introduction, of this imrove ment, the operation of glazing, although sufficiently well, was somewhat tedious, being effect ed almost exclusively by the mere application of manual labour. It was performed upon a table, the cover of which was oblique to the horizon, forming with it an angle of 15° or 20?. The cloth being stretched on this, and a quantity of wax being thinly spread on its surface, the glazing was effected by the reciprocation of a smoothed flint, vibrating at the end of • a rod, somewhat similar to the oscilla tions of a pendulum. The centre of oscillation was also moveable on a spring, in order to reduce the arc of vibration to a plane, and keep the flint in uniform contact with the cloth. But a man's power was competent to glaze only. a few inches in breadth at once, and it was only by successive shillings, that the whole breadth was successively brought under the friction of the flint. The glazing calender pro duces the same effect, with increased uniformity, simply by changing the relative velocities of the cy linders to each other, and generating friction, as well as pressure, at the points of contact.