�ri^lil above the plane which [insses Ibrougli wnpperetlf«s of lli« orbits ami the oriflcea of the Cius. Mr. Galton adds, that while writing his ae- ciiunt, insinimenti fnr head ineasurements were being eolidij conatructed for him, whieh will be in iiw In Csinbrldge. Eng.. in ISS^.
��THE STA TVS OF AERONA UTICS IN ISHi-
UcnoY DB Brdionac, member of the French tiocMvi de* ing^aititirs ckiU. has recently presented to Uiat aeeociation a very eomplete yet eoncise TJipifi at the present stale of the art of aeronautics. ejpecl«ily m related to the general ayslem of ' dirige- able- aeroi.tals. The first indlcatiuus of sui'cess are assiuneil tn hare been given by the experiments of Giflard (1852-55), Dupuy tie Lflme (1371), iind Tls. sandier and Renard and Krebs (recently). The tjrst coDdltloQ is considered to be etftbility, retaialng the relative position of parts seen in the earlier balloons.
Giflanl. in his earliest attempts, Utftined it speeil of three, and later of four, metres per second, Diipuy de LAme, and Henard Hiid Krebs, have used bifiler forms of balloon, and have secured more rtgldity of structure; hut ii<me have obtained high speed.
Extreme lightness of motor is a vitally essential feature ; and the best that has yet been done is iUiiitnI«il by the steam-engliips of Thomeycroft, weighing about 33 kilograms (73 pounds) p«r horsc' {tower, ami which, by sacrifleing economy of fuel, U i* Uiou^'ht possible may be reduced lo 20 kilos (44 pounds), and the various storage and other bat- lOiM yielding electricity, which, aceonling to TIbshii- dier, may be reduced to a weight nut exceeding '& IdhM (K pounds) per horse-power. Messrs. Itenard ■ad Krebs clalro a vreight as low us IT or IS kilos. Tba experiment of Tlssandler In 138-'). in the appll- eatlon of electricity to this work, is thus expected to iMd to osefnl results.
Tbe propelling iiKtrument is always the screw. Its position is a matter ot hnportance. As usually arranged, it has a tendency to cause vertical devla- tiotiB of the machine, which are objectionable. It fi boped that it may prove possible to place the •crew-sbafi in line »ith the axis ot syminelry of the balloon. Id order to avoid this dlRlculty. This may b« done by setting it between a pair of spindlo- ■hiqted supporting balloons. 1 1 is uncerLiin whether it will be found best to place it ahead or astern of ttic balloon; but it is presumed best at the stern. TbA screw is objectionable on the score of its low efflcleacy. — about 0.30 (?); but nothing belter has jrel been devised.
Bmignoc proposes a formula by menns of which to caiculat« the resistance of the aerostat, and by ita application determines the relative reslslancea of the maehines of the several aeronauts whose work has been mentioneil, as follows; Qlllard, 1852, 0.(^76; GIffard, ISH, 0.03.".; Uupuy de LOme, 0.16; Tlssan- dier, 0.1^: Jtenard and Krebs (1), ll.l^; lienard and Krebs f2f, ".'li. In Ibe last Iwoo.ises, the large unJ
��the smalt ends of the vessel are calculated sepa>
The speeds actually obtained by thein were Xi.h iiielres per second by the last named, and from 3 to 4 metres by their predecessora. Had the former driven their machines with the small end ahead, instead of the larger end, as octuotiy practised, the critic calcu- lates that they might have obtained a speed ot nearly ten metres, A symmetrically formed cylindriciil .ipindle is advised as the probably best form for the body of the air-ship, inserting a straight middle body when constructing very large vessels. Tlie larger the machine, the lighter, comparatively, will be the driving machinery. The substitution of sup- porting hoods, sheets, or tissues, for cords, may assist in Ihe endeavor to reduce resistances. The loss of gas by leakage can be reduced by choice ot proper material for the balloon. The waste of gas in ascend- ing and descending ronst be avoided, and may, per- haps, be obviated altogether. This becomes an easier matter in ascents of the kind here contemplated. In which no greater height will be sought than is suffi- cient to clear obstacles safely: probably a hundred metres will prove ample. For such work, the altei^ nate compression and expansion ot liie adjusting volume of gas wilt probably suffice.
The conclusion is reached that the art of aerosta- tion is much nearer a practically applicable state than scientllic men generally suppose. The objects now sought are the allainment of better and mors stable forms, the more eDeclive arrangemenl of parts, the Invention of lighter motors, invariable in weight, and convenient of operation, and the securing ot higher efficiency o( propelling InsinimenL Even now, with the experience ot Ihe past, it is possilde to build a machine of this clau capable of making at least ten metres per second through the surrounding
Thera conclusions of Bnilguac are especially in- le resting when compared with those of Pole as presented to lUe Bt^Iish institution of civil engi- neers. In which he finds that the supporting' power of the balloons adopted by the aeronauts above men- tioned, and the driving-power and weight!! ot the torpedo-boat enghies of British makers, are such as should permit the construction of an air-ship four hundred feet long, to travel at the rat« of thtrtr miles an hour. II. H. TutritsTnx.
��FlNDJSa A BOKE-llOLi:.
Two novel and ingenious melhotis ot locaiing the position of a bore-lude have recently been describeii ill the London Enginterinti. In the ftrsl case, at Edinbni^h, it was desireil to connect the lower end ot a bore-hole, two liundred feet deep, with a well some eighteen feet distant. A drift run In Ihe sup- posed direction failed to strike the hole, although much rock was cut away, and It was evident that the drill had deviated consiiliTably from Ihe vertical. After ;in iinsuccesstui iittenipt lo l.io;iti- Ms direclioiL
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