I have written, he will find, that the theorems are based on the principle, that the opposing forces-namely, gravity and friction on one side and steam power on the other are in equilibrio, not one in excess of the other; and, consequently, that the acceleration and retardation Iver M'Iver presumes, has here no existence. The effects of changing the velocity, by changes in the inclination, are in the present instance supposed to balance each other; and the extra times in getting up and losing the velocity at the termini are likewise neglected, because the conditions for their determination could not well be taken into account in the general estimates of the expense and time of transit. He will also find that the formulæ are not given as mathematically, but practically true, limited in the application, not from any defect in them but from other considerations, to practical ascents, and to such descents as full steam can be applied to with a safe velocity. That there are other matters to be investigated to render the subject complete, and which, had not various causes interposed, I should before now have taken up, I admit, but the want of them does not disturb the general accuracy of the theorems I have given as rules of computation. My object has been to simplify the theory of locomotive transit as much as I could, and to reduce one or two points in that theory to calculable rules, which I apprehend the ordinary principles of science could never have compassed. Whether I have succeeded or not, experiments alone can determine. I cannot say I have any appre hensions on the subject; but, instead of discussion, I should be happy to see an extensive series of experiments undertaken. These would do the cause of locomotion a real good, whatever they prove or disprove.

Kensington, Oct. 1835.

JOHN HERAPATH.

ON FIRE PROOF BUILDINGS. BY MR. CHRISTOPHER DAVY, ARCHITECT. (In continuation from last vol. p. 500.) Lord Stanhope's method of "double underflooring "is very similar to that described in my last communication. The fillets and short pieces of laths are laid and fixed precisely in the same manner, but the coat of rough plaistering is not

recommended to be more than half as thick, as that applied in the method of "single underflooring," because a layer of plaister is, in the present case, spread upon the top, upon which is bedded another series of laths as before; a coat of the same kind of plaister is afterwards spread and well trowelled upon the top of the second series of short laths level with the top of the joists, and, it is stated, that the sooner done the better.

The following observations are equally applicable to " single and double underflooring."

Common coarse lime and hair may be used, but it is considerably cheaper, and even better, in all cases, to make use of hay instead of hair, in order to prevent the plaister from cracking. The hay should be cut to about three inches in length, but not shorter. The proportions of the ingredients are one measure of common rough sand, two measures of slacked lime, and three measures, but not less, of chopped hay. They are to be beaten up together in the manner of common mortar. It is recommended that the hay should be well dragged and intermingled with the composition; at the same time, it ought never to be put in till the other two ingredients are well beat up together with water. This rough sort of plaister ought never to be made thin; the stiffer it is the better," says Lord S., "provided it be not too dry to be spread properly upon the laths."

As flooring boards require, in many instances, to be laid soon, we may then adopt a different mode, no less simple and equally efficacious. His lordship states, that he had adopted it in a very extensive work with the greatest advantage. A fourth or fifth part of quick lime in powder is to be well mixed with the rough plaister, which will cause the composition to dry with great rapidity. His lordship recommends as the easiest method of reducing the quick lime to powder, to drop a small quantity of water on the lime-stone a short time before the powder is intended to be used, when the Îime will by this process have acquired heat quite sufficient for the purpose.

When the rough plaister-work between the joists has become thoroughly dry, it ought to be re-examined carefully, in order to stop such cracks or flaws in the work as may have arisen from accident. If any should be discovered, it is recommended that a mortar-wash or light grout

ing should be washed into such parts with a plaisterer's brush. The mortarwash to be prepared as follows:-Provide about two measures of quick-lime and one measure of common sand; amalgamate these well with water; continue the process till the water grows thick, or to the consistence of a thin jelly: this, when used, will dry in a few minutes.

Previous to the flooring-boards being laid, a small quantity of very dry common sand should be strewed over the rough plaister-work, always excepting the tops of the joists. The sand should be struck smooth with a hollow rule, which ought to be about the length of the distance from joist to joist, and camber or curve in the centre about one-eighth of an inch. By applying this rule, we cause the sand to lay rather rounding in the middle of the interval between each pair of joists; the flooring-boards may then be laid in the usual manner, but particular attention must be paid to the rough plaister-work, sand, &c., being perfectly dry before the boards are laid; for fear of the dry rot, of which however, there is no kind of danger when this precaution is made use of.

It

Underflooring is also applied with the utmost success to wooden staircases. is made to follow the shape of the steps, but no sand is laid upon the rough plaisterwork in this case.

Extra Lathing is a term used when greater security is required for ceilingjoists or sloping (such as mansard or curb) roofs, and is simply this: when the laths are ready to be nailed on, some of the above-mentioned rough plaister should be spread between these laths and the joists (or other timbers), against which these laths are to be nailed close to each other. When either of the ends of any of the laths lap over other laths, it ought to be attended to, that these ends be bedded sound in some of the rough plaister This attention is equally necessary for the second layer of laths hereafter mentioned. The first layer of laths should be covered with a thick coat of rough plaister; the second layer of laths are then to be nailed on, each lath as it is put on being well squeezed and bedded sound into the soft rough plaister. For this reason, no more of the first coat ought to be laid on at a time, than can be immediately followed with the second layer of laths. The second layer of laths ought to be laid as close to each other as possible, to

allow of a proper clench for the rough plaister. The second layer may be then plaistered over with a coat of the same kind of rough plaister, or it may be plaistered over in the usual manner.

Treble Lathing may be used, but is seldom required.

Intersecuring is similar, in many respects, to underflooring, but no sand is required to be laid upon it. Intersecuring is applicable to the same parts of a building, as the method of extra lathing before described, but its application is only required occasionally.

C. DAVY, Architect.

3, Furnival's Inn, Oct. 10, 1835. (To be continued.)

METROPOLITAN STREET-PAVING.

Sir, The improvement of street-påving on inclinations having very justly attracted the attention of some of your correspondents, I beg to offer a few observations on the subject. Mr. Davy in his letter of the 5th ult., referring to the mode of pitching adopted on Fish-street Hill, says, "certain destruction awaits the knees of any animal that may fall upon its ridged surface," &c. This, doubtless, is true to a great extent; but as long as the new pavement is kept in a good working state, there is scarcely any fear of a fall, except in descending; and as I am persuaded the plan is a good one for ascending an inclination, I would suggest that, in altering the pavement of Holborn-hill, or of any other general thoroughfare, only one-half, that is the near side going up, should be pitched in the new manner. This appears to me to be necessary, for if the descending side were pitched like Fish-street Hill, stagecoaches, &c. could not use drags; neither could a coachman pull up his horses with any reasonable facility; because horses could not slide in stopping, as they do at present; and if a horse did come down, he would, as Mr. Davy observes, be ruined. The traffic on Fish-street Hill and Cow-lane has, I understand, very considerably increased since those hills have been pitched in the present manner; notwithstanding which, the number of accidents has greatly diminished. Formerly horses were down, particularly on Fish-street Hill, almost every hour; now a fall is quite a novelty. "T. C." in his letter of the 19th ult. speaks of the "new

I have written, he will find, that the theorems are based on the principle, that the opposing forces-namely, gravity and friction on one side and steam power on the other are in equilibrio, not one in excess of the other; and, consequently, that the acceleration and retardation Iver M'Iver presumes, has here no existence. The effects of changing the velocity, by changes in the inclination, are in the present instance supposed to balance each other; and the extra times in getting up and losing the velocity at the termini are likewise neglected, because the conditions for their determination could not well be taken into account in the general estimates of the expense and time of transit. He will also find that the formulæ are not given as mathematically, but practically true, limited in the application, not from any defect in them but from other considerations, to practical ascents, and to such descents as full steam can be applied to with a safe velocity. That there are other matters to be investigated to render the subject complete, and which, had not various causes interposed, I should before now have taken up, I admit, but the want of them does not disturb the general accuracy of the theorems I have given as rules of computation. My object has been to simplify the theory of locomotive transit as much as I could, and to reduce one or two points in that theory to calculable rules, which I apprehend the ordinary. principles of science could never have compassed. Whether I have succeeded or not, experiments alone can determine. I cannot say I have any apprehensions on the subject; but, instead of discussion, I should be happy to see an extensive series of experiments undertaken. These would do the cause of locomotion a real good, whatever they prove or disprove.

Kensington, Oct. 1835.

JOHN HERAPATH.

ON FIRE PROOF BUILDINGS. BY MR. CHRISTOPHER DAVY, ARCHITECT. (In continuation from last vol. p. 500.) Lord Stanhope's method of "double underflooring is very similar to that described in my last communication. The fillets and short pieces of laths are laid and fixed precisely in the same manner, but the coat of rough plaistering is not

recommended to be more than half as thick, as that applied in the method of "single underflooring," because a layer of plaister is, in the present case, spread upon the top, upon which is bedded another series of laths as before; a coat of the same kind of plaister is afterwards spread and well trowelled upon the top of the second series of short laths level with the top of the joists, and, it is stated, that the sooner done the better.

The following observations are equally applicable to "single and double underflooring."

Common coarse lime and hair may be used, but it is considerably cheaper, and even better, in all cases, to make use of hay instead of hair, in order to prevent the plaister from cracking. The hay should be cut to about three inches in length, but not shorter. The proportions of the ingredients are one measure of common rough sand, two measures of slacked lime, and three measures, but not less, of chopped hay. They are to

be beaten up together in the manner of common mortar. It is recommended that the hay should be well dragged and intermingled with the composition; at the same time, it ought never to be put in till the other two ingredients are well beat up together with water. This rough sort of plaister ought never to be made thin; the stiffer it is the better," says Lord S., provided it be not too dry to be spread properly upon the laths."

66

As flooring boards require, in many instances, to be laid soon, we may then adopt a different mode, no less simple and equally efficacious. His lordship states, that he had adopted it in a very extensive work with the greatest advantage. A fourth or fifth part of quick lime in powder is to be well mixed with the rough plaister, which will cause the composition to dry with great rapidity. His lordship recommends as the easiest method of reducing the quick lime to powder, to drop a small quantity of water on the lime-stone a short time before the powder is intended to be used, when the lime will by this process have acquired heat quite sufficient for the purpose.

When the rough plaister-work between the joists has become thoroughly dry, it ought to be re-examined carefully, in order to stop such cracks or flaws in the work as may have arisen from accident. If any should be discovered, it is recommended that a mortar-wash or light grout

ing should be washed into such parts with a plaisterer's brush. The mortarwash to be prepared as follows:-Provide about two measures of quick-lime and one measure of common sand; amalgamate these well with water; continue the process till the water grows thick, or to the consistence of a thin jelly: this, when used, will dry in a few minutes.

Previous to the flooring-boards being laid, a small quantity of very dry common sand should be strewed over the rough plaister-work, always excepting the tops of the joists. The sand should be struck smooth with a hollow rule, which ought to be about the length of the distance from joist to joist, and camber or curve in the centre about one-eighth of an inch. By applying this rule, we cause the sand to lay rather rounding in the middle of the interval between each pair of joists; the flooring-boards may then be laid in the usual manner, but particular attention must be paid to the rough plaister-work, sand, &c., being perfectly dry before the boards are laid; for fear of the dry rot, of which however, there is no kind of danger when this precaution is made use of.

Underflooring is also applied with the utmost success to wooden staircases. It is made to follow the shape of the steps, but no sand is laid upon the rough plaisterwork in this case.

Extra Lathing is a term used when greater security is required for ceilingjoists or sloping (such as mansard or curb) roofs, and is simply this: when the laths are ready to be nailed on, some of the above-mentioned rough plaister should be spread between these laths and the joists (or other timbers), against which these laths are to be nailed close to each other. When either of the ends of any of the laths lap over other laths, it ought to be attended to, that these ends be bedded sound in some of the rough plaister This attention is equally necessary for the second layer of laths hereafter mentioned. The first layer of laths should be covered with a thick coat of rough plaister; the second layer of laths are then to be nailed on, each lath as it is put on being well squeezed and bedded sound into the soft rough plaister. For this reason, no more of the first coat ought to be laid on at a time, than can be immediately followed with the second layer of laths. The second layer of laths ought to be laid as close to each other as possible, to

allow of a proper clench for the rough plaister. The second layer may be then plaistered over with a coat of the same kind of rough plaister, or it may be plaistered over in the usual manner.

Treble Lathing may be used, but is seldom required.

Intersecuring is similar, in many respects, to underflooring, but no sand is required to be laid upon it. Intersecuring is applicable to the same parts of a building, as the method of extra lathing before described, but its application is only required occasionally.

C. DAVY, Architect.

3, Furnival's Inn, Oct. 10, 1835. (To be continued.)

METROPOLITAN STREET-PAVING.

Sir,-The improvement of street-påving on inclinations having very justly attracted the attention of some of your correspondents, I beg to offer a few observations on the subject. Mr. Davy in his letter of the 5th ult., referring to the mode of pitching adopted on Fish-street Hill, says, "certain destruction awaits the knees of any animal that may fall upon its ridged surface," &c. This, doubtless, is true to a great extent; but as long as the new pavement is kept in a good working state, there is scarcely any fear of a fall, except in descending; and as I am persuaded the plan is a good one for ascending an inclination, I would suggest that, in altering the pavement of Holborn-hill, or of any other general thoroughfare, only one-half, that is the near side going up, should be pitched in the new manner. This appears to me to be necessary, for if the descending side were pitched like Fish-street Hill, stagecoaches, &c. could not use drags ; neither could a coachman pull up his horses with any reasonable facility; because horses could not slide in stopping, as they do at present; and if a horse did come down, he would, as Mr. Davy observes, be ruined. The traffic on Fish-street Hill and Cow-lane has, I understand, very considerably increased since those hills have been pitched in the present manner; notwithstanding which, the number of accidents has greatly diminished. Formerly horses were down, particularly on Fish-street Hill, almost every hour; now a fall is quite a novelty. "T. C." in his letter of the 19th ult. speaks of the "new

I have written, he will find, that the theorems are based on the principle, that the opposing forces-namely, gravity and friction on one side and steam power on the other are in equilibrio, not one in excess of the other; and, consequently, that the acceleration and retardation Iver M'Iver presumes, has here no existence. The effects of changing the velocity, by changes in the inclination, are in the present instance supposed to balance each other; and the extra times in getting up and losing the velocity at the termini are likewise neglected, because the conditions for their determination could not well be taken into account in the general estimates of the expense and time of transit. He will also find that the formulæ are not given as mathematically, but practically true, limited in the application, not from any defect in them but from other considerations, to practical ascents, and to such descents as full steam can be applied to with a safe velocity. That there are other matters to be investigated to render the subject complete, and which, had not various causes interposed, I should before now have taken up, I admit, but the want of them does not disturb the general accuracy of the theorems I have given as rules of computation. My object has been to simplify the theory of locomotive transit as much as I could, and to reduce one or two points in that theory to calculable rules, which I apprehend the ordinary principles of science could never have compassed. Whether I have succeeded or not, experiments alone can determine. I cannot say I have any appre hensions on the subject; but, instead of discussion, I should be happy to see an extensive series of experiments undertaken. These would do the cause of locomotion a real good, whatever they prove or disprove.

Kensington, Oct. 1835.

JOHN HERAPATH.

ON FIRE PROOF BUILDINGS. BY MR. CHRISTOPHER DAVY, ARCHITECT. (In continuation from last vol. p. 500.) Lord Stanhope's method of "double underflooring "is very similar to that described in my last communication. The fillets and short pieces of laths are laid and fixed precisely in the same manner, but the coat of rough plaistering is not

recommended to be more than half as thick, as that applied in the method of "single underflooring," because a layer of plaister is, in the present case, spread upon the top, upon which is bedded another series of laths as before; a coat of the same kind of plaister is afterwards spread and well trowelled upon the top of the second series of short laths level with the top of the joists, and, it is stated, that the sooner done the better.

The following observations are equally applicable to "single and double underflooring."

Common coarse lime and hair may be used, but it is considerably cheaper, and even better, in all cases, to make use of hay instead of hair, in order to prevent the plaister from cracking. The hay should be cut to about three inches in length, but not shorter. The proportions of the ingredients are one measure of common rough sand, two measures of slacked lime, and three measures, but not less, of chopped hay. They are to be beaten up together in the manner of common mortar. It is recommended that the hay should be well dragged and intermingled with the composition; at the same time, it ought never to be put in till the other two ingredients are well beat up together with water. This rough sort of plaister ought never to be made thin; the stiffer it is the better," says Lord S.," provided it be not too dry to be spread properly upon the laths."

As flooring boards require, in many instances, to be laid soon, we may then adopt a different mode, no less simple and equally efficacious. His lordship states, that he had adopted it in a very extensive work with the greatest advantage. A fourth or fifth part of quick lime in powder is to be well mixed with the rough plaister, which will cause the composition to dry with great rapidity. His lordship recommends as the easiest method of reducing the quick lime to powder, to drop a small quantity of water on the lime-stone a short time before the powder is intended to be used, when the Îime will by this process have acquired beat quite sufficient for the purpose.

When the rough plaister-work between the joists has become thoroughly dry, it ought to be re-examined carefully, in order to stop such cracks or flaws in the work as may have arisen from accident. If any should be discovered, it is recom mended that a mortar-wash or light grout