the words "not being contrary to law" as a separate and distinct condition, unconnected with the following one, of its being "mischevous to the state," to which alone the subsequent definitions really refer. And this point was slightly touched upon in the argument between the second learned counsel, on the part of the appellant, and one of their Lordships, although not dwelt upon or noticed in the judgment, their Lordships feeling themselves apparently precluded by the authority of Roebuck's case, or that it was not necessary for them, after that, to go into any collateral points.

It may have appeared somewhat presumptuous in the writer of these remarks thus to impugn the validity of all existing grants, since the law officers of the Crown have not deemed it necessary (not even since the above decision has been publicly known) to make any alteration in the forms of patents, for they continue to be issued, with the proviso as to novelty, in the same words as heretofore. Possibly this may have arisen from inattention, or from a desire not to prejudge the question, to which allusion has been made.

It cannot but be felt by all owners of patents, that this doubtful state of the law, or suspicion, if it be no more, of the invalidity of existing grants, is very unsatisfactory, and that it would be extremely desirable that all doubts should be got rid of during the ensuing session. Might it not afford also a good opportunity for amending the present inconvenient practice of requiring three separate grants for the three sections of the Kingdom? Surely the same stamps and fees might be retained and paid on a single grant, (if that be the obstacle,) just as they are now exacted on the three grants, leaving the patentee the same option which he now has, of having such grants made out for one, two, or three countries.

Scientific Notices.

REPORT OF TRANSACTIONS OF THE INSTITUTION OF CIVIL ENGINEERS.

(Continued from page 314, Vol. XXI.)

Mr. Farey remarked, that it would lead to an incorrect appreciation of the merit of the new indicating instrument, if it were to be considered merely as a substitute for the ordinary indicator, when in fact they were two instruments, adapted to and equally useful for different purposes.

The new instrument does not preserve any record of the minute details of any one stroke, like the ordinary indicator, but it records a true aggregate of all the details of any number of succeeding strokes it gives the same results as would be obtained if it were possible to have two ordinary indicator cards correctly taken, at each succeeding stroke of the engine, during the whole time of observation, by means of two indicators, one of them applied to the upper, and the other to the lower end of the cylinder; and also provided, that an accurate admeasurement of every one of all those cards was afterwards made, at ten places, in the length of the card, by the scale of pounds per square inch, in the usual manner, and the amount of the ten measurements added into one sum, and then (without averaging each card) that such sum of each card should be carried to a continuous account, to obtain a grand sum total, representing all the force that had been exerted, during both halves of every stroke made throughout the experiment, reckoned at ten stages or portions of the length of stroke.

Such a grand total of all the cards would be a number representing the same fact, as is represented by the number shown by the new instrument; and would therefore be dealt with, in each case, in a similar manner, as one of the data (viz., that representing force) for calculating (by aid of other data representing motion or space) the whole power exerted during the time of observation.

In trying the performance of a steam-vessel, alternately up and down the measured mile in the river Thames, along the shore of Dartford marshes, it is usual to take an indicator card from each engine, at every such run and by summing up each card, some difference will be found between them, wherefore an average of the results of several cards will give more authentic information respecting the force exerted by the engines during the whole trial, than could be obtained if one such card aloue had been depended on. The new instrument takes cognizance of every stroke that is made by the engine during the whole time of observation; and in cases (such as in the Great Western steamer) where a considerable variation of force in succeeding strokes occurs frequently during such time, it is a desideratum to obtain

the results which this instrument is intended to give, and which, as far as it has been tried, it seems likely to give with fidelity.

The instrument, when applied as it had been at Old Ford, becomes another mode of ascertaining performance, similar to what is reported monthly, respecting the engines in Cornwall, but not exactly the same as is there called "duty," because the new instrument would show the aggregate of the unbalanced force that had been exerted (during a given time) by the steam to impel the piston; whilst the monthly reports shew (by load in pounds, length of stroke in pumps, and number of strokes made), the aggregate of force exerted in the same time, in overcoming the resistance that the mere hydrostatic weight of the columns of water in the pumps opposes to the motion of the engine.

The instrument ought always to show more force than the reports do, and the difference between the two would be the aggregate of all the force that had been lost, during the time, by friction of the moving parts of the engine, pumps, &c.

Respecting that loss of force, there is no more of it than arises from such friction, from working the air-pumps, &c., and from resistance of the water; but it is wholly a mistake to suppose that any such loss is augmented by producing motion. Professor Moseley had just stated the true theory on that head, which theory was demonstrable mathematically, and admitted of no question.

It would be needless to go further into what had been so well explained, except to observe, that the theory applies, without the least abatement or modification, by incidental causes, to the case of any machine which, like a steam-engine, regains the same state, as to rest, (or as to motion,) at the end of the time of observation upon it, as the state in which it was at the commencement of that time; and the theory shows that, in such a machine, no part of the force, exerted upon it, (or exerted by it,) can have been expended, or lost, in producing motion, whatever may be the number or the extent of changes or variations in velocity of motion that the machine had undergone during the time of observstion; for although force must be exerted to produce motion

from a state of rest, yet all force, that is so exerted, will be rendered back again, when the motion, which was produced, has ceased, and the state of rest regained: in the steam-engine that is the case at the termination of every half stroke.

Respecting trials, by means of the smallest force of steam, which will just press the piston of a pumping-engine slowly down in the cylinder, or cause the engine to come creeping in-doors : they are not much to be depended upon, as evidence of the force that is actually lost in overcoming friction; first, because no steadiness of exhaustion can be kept up beneath the piston, nor steadiness of steam above the piston, whilst the engine is so treated, and also because the counter-weight of engines in Cornwall is not apportioned with any great nicety. In general they are worked with more counter-weight than is requisite, and but little loss is occasioned by so doing; for if the counter-weight is unnecessarily great, so as to carry the engine quick out of doors, (that is, to cause the pump-rod to descend briskly,) then the equilibriumvalve is closed sooner, and therefore retains more steam between the top of the piston and the cover of the cylinder, in what has been called the steam-cushion, which stops the descending motion of the pump-rod; and in consequence of more steam being reserved in such cushion, to go towards the supply for the succeeding stroke, that increase in the reserved steam, compensates, in part, for the waste of force occasioned by the redundancy of counter-weight, which caused the quick motion.

Mr. Farey had received from Mr. John Taylor, indicator cards of Taylor's engine at the United Mines; one card was taken soon after it was first set to work, with an extravagant counter-weight; another card was taken immediately after several tons of balance had been added, without alteration of the load of water in the pumps. Balance in Cornwall is contrary to counter-weight, so that adding balance, effects a reduction of counter-weight. Now if an attempt had been made to ascertain the friction of that engine, by trying what strength of steam would cause the engine to creep in-doors, the day before the balance was added, the friction would have appeared (by that mode) to have been 3 lbs. or 4 lbs. 2 M

VOL. XXI.

per square inch greater than it would have appeared to be after the balance had been added; although that was an extreme case, not likely to occur often, yet errors in the imputed amount of friction, to the extent of 1 lb. or 14 lb. per square inch, would be continually made, if dependence were to be placed on that mode of trial of engines, working with so much counter-weight as they may happen to have.

The friction of modern engines in Cornwall, including that of their pit-work and pumps, and the resistance of the water, he believed would not be found materially, if any, greater than was the case in Mr. Watt's old engines, when the depth of the mines was not half as great, and the weight of moving parts not one-third as great; for the improvement in pit-work and pumps, and enginework, had kept pace with that increase of depth and weight.

The pump-rods are hung more truly perpendicular, and the lengths of timber for the rods are better jointed, so as to cause them to hang straighter in the pit whilst working, and avoid lateral vibratory flexure, and therefore the rods rub less against their guides; the plungers are set truer, and, being of large diameter, have less rubbing surface in proportion to their contents, the lifts being higher, and short lifts being avoided: these and many other improvements tend to reduce the friction in proportion to the force exerted.

The small quantity of steam expended, and consequently of water injected into the condensers, as well as better joints to prevent leakage of air into the exhausted parts, reduces the power required to work the air-pump to a smaller proportion of the power exerted by the engine than formerly. And, in particular, the valves and water-ways, through the pumps, are made more open than formerly, so as to diminish the loss of force that is occasioned by resistance of the water; that loss of force, by resistance, increases as the square of the velocity of the motion, when loss of force, by mere friction, does not increase by increase of that velocity. He believed few large engines in Cornwall, which are making what is now thought tolerably good performance, lose more than at the rate of 3 lbs. per square inch of the