244 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[August, 



" A cobeorn mortar was placed 100 yards from six new deal targets laid 

 on the ground, and two new nadmill tilts spread out near them, to estimate 

 by the iniprcssion made im tlicm the force with which the balls would fall. 



The first round was with the usual tin case, containing 33 four ounce-balls, 

 with a charge of one ounce of powder, elevation 45°. The case went bodily 

 about 130 yards without breaking. 



Loose balls were then jut in over a wooden bottom. After a number of 

 rounds with the above charge and elevation, with different numbers of four- 

 ounce balls, it was asccitaintd tlat the cohl-orn would throw 42 of them 100 

 yards, and that the spread was, on an average, about 10 or 12 yards. It 

 was not very easy to liit the targets and cloths, altliough they covered a 

 surface of 774 square feet; but, in one instance, 22 balls lelt their mark. 

 The indentation on tlje surface of the deal was «o small that it could not well 

 be measured — it ccilainly was not mure than -^^^ of an inch dcfp. A hall 

 thrown with force from the hand appeared to make an (qnal imiression. 

 Those which struck the wadnjill tilt did not penetrate, but merely indented 

 the ground underneath. The penetration of the halls into the ground (hIucIi 

 was of the softest nature of meadow) was, on an average, 2 inches ; but the 

 balls thrown by hand did not penetrate so far. 



The mortar was then elevated to 75^, and with two ounces of powder and 

 42 balls made nearly the range as before ; but the spread was increased to 

 about 40 yards, so that it was difficult to hit the surface aimed at. Several 

 balls did, however, at length fall on the targets and warimill lilts. The im- 

 pression on the former was something increaseil.but still so trifling as hardly 

 to be measured ; the halls did not go through the cloth, and the penetration 

 on the meadow was only increased to about three inches."' 



Secondly, to determine the dimensions of the balloons necessary to raise 

 the weights proposed by Mr. Warner. 



By a well-known principle of pneumatics, the weight of the balloon and 

 its appendages, when floating in the air in equilibrium, is equal to the weight 

 of the air displaced. Now the density of hydrogen gas when prepared in 

 large quantities for the purpose of inflation is about -2, or a cubic foot « eighs 

 •2 oz. In order to ascertain the density of the air, the diminution of baro- 

 metric pressure due to the altitude must be taken into account ; and if the 

 balloon be supposed to have attained the average altitude of 2500 feet, the 

 density of the air may be taken at 1-09, or a cubic foot of air weighs 1-09 oz. 



Assume the balloon to be spuerical, and call its radius »•. Its solid content 

 = 4»r3 = 4-1887 xr\ 



The weight of that volume of gas = -2 x 4-1887 x r^. 



The weight of that volume of air = 1-09 x 4-1887 x r\ 



The weight of 100 shells of 500 lb. each = 800,000 oz. 



The weight of silk, netting, car, &c., taken for an approximate determina- 

 tion of the size of the balloon, = 73,931 oz. 



Now, as has been stated, the total weight raised is the same as that of 

 k Tolume of air equal to the capacity of the balloon, &c. Hence, neglecting 

 the space occupied by the car and appendages, we have the equation 



1-09x4-1887 j-3=..2x 4-1887 t^-i- 800,000 -^ 73,931. 

 Whence may be obtained the following results: — 

 4-1887 »-3 =981,945 (volume) 



r = I61-G02 (radius) 

 4 jrr2= 47,686 (surface) 



In other words, the capacity of the balloon and the quantity of gas which 

 would be required to inflate' it would be nearly one niillwn cubic ftel, the 

 quantity of silk required in its construction would Wforty-eiyht thousmid 

 $quarefeet, and its diameter (double the radius) one hundred and (wenty. 

 three feet. 



If instead of ascertaining the dimensions of the balloon at an altitude of 

 2500 feet, its dimensions necessary for raising the given weight just off the 

 ground he calculated, the results will not be materially altered. In this case, 

 the density of the air must be taken at 1-2 (instead of 1-09), and the diame- 

 ter of the balloon will be found to be 1 19 feet instead of 123 feet. The fol- 

 lowing table shows the dimensions of the balloon necessary for sustaining 

 the several specified loads, and the cost of the silk required in its construc- 

 tion. 



WICKET-GATE FOR CANAL LOCKS. 



Invented by F. C. Lovtthorp, Esq., C.E., of Pennsylrania, United 

 Slates. (Reported in the Franklin Journal.) 



The object of the apparatus is to draw water rapidly from a higher level 

 to a lower ; for example, to fill or empty lock chambers, or to draw olT a 

 canal level, mill race, or reservoir of any kind. It is effected by an inge- 

 nious application of hydrostatic pressure. In the efiiuent sluice is placed 

 a gate, or wicket, with two leaves at right angles to each other, having a 

 cross-sectiou like the letter L, one leaf being longer than the other. This 

 gate works upon pivots, or a hinge, at the angle of intersection of the two 

 leaves, and at one side of the sluice. The shorter leaf of the gale is of 

 proper dimensions to close the sluice when the floiv of water is not 

 required. This leaf is kept shut by the pressure of the head of water, 

 which produces no effect upon the longer leaf so long as it is admitted 

 freely to both sides of it. 



When the sluice is to be opened, the water is drawn from 'one side of 

 the longer leaf, and immediately the pressure upon the other side prepon- 

 derates against the shorter leaf, and forces it open. The opposite effect is 

 produced by admitting the water to both sides of the longer leaf, when the 

 pressure upon the shorter leaf again close s the sluice. The--e alternate 

 effects are prnduced by two small turning wickets at right angles to each 

 other and coupled together, which are moved simultaneously by a single 

 lever. 



The time and effort required to manoeuvre the small wickets will cer- 

 tainly not he greater than is necessary to work one of the simple turning 

 wickets generally used in lock-gates, while the quantity of water discharged 

 by the sluice will, with the above proportions, be about four-fold, and may, 

 by a variation of the relative dimensions of the parts, be even greatly 

 increased. 



• Ibe silk of wbicli balloons are made is of the best quality, and ocly 24 Inches wide 

 •o tlrat a corresiionding iocrease must be made. 



Fig. 1 is a plan, in which the part A is intended to represent a reservoir, 

 lock-chambtr, &c. «,(/, shows the leaves of the wicket-gute (which is 

 supposed to be placed lu the tide wall of a lock), both oi which i«re se- 

 cured to the shaft s, aud are connected by means of the rods, or bars, p p. 

 H is a recess or chamber, into which the leal d moves lu upeumg the leaf 

 or gate o. i, o, are smull valve gates (so connected or cuupled, that both 

 may be turned at tbe same time, the oue opening, arid the oiher shutiiog), 

 used /or emptying and filling the cliamber H, and may be worked as sbovvo 

 in the plan and sectional views (figs. 1,'J, 3), or otherwise. c c is a clian- 

 j^el or pipe, cuiniuunitating with ihe water m the lock-chamber or reser- 

 oir A, and the chamber 11, through the valve-gate i. /if is a grating 



