June 15, 191 1] 



NATURE 



521 



The chief features of the building are shown in 

 Fig. I. The main waterway is 30 feet wide, 12 feet 

 3 inches deep, and 500 feet 'long, clear of beach and 

 ■ docks, the latter being for storing models and for allow- 

 ing access to them for ballasting and trimming pur- 

 poses. The walls and floors are of concrete varying 

 from 2 to 3 feet in thickness, except at the shallow 

 docks, where the sides are 7 inches I'einforced con- 

 crete. 



A large steel carriage for towing the models has 

 been erected across this waterway. It runs upon four 

 wheels on rails which are bolted to continuous iron 

 supports secured to the tops of the concrete walls. 

 This carriage is driven by four motors — one over each 

 wheel — the necessary power being obtained from con- 



about 2 inches in thickness, the length being generally 

 20 feet, but varying according to the form. The 

 paraffin wax is melted in a large tank through which 

 hot water is circulated in pipes, and back tlirougli the 

 surrounding casing, and the wax drawn off through 

 pipes mto a clay mould prepared to the shape of the 

 model, but with an allowance of about a quarter of 

 an inch for finishing. 



The model when set is transferred to the shaping 

 machine (Fig. 2). This machine works on the copying 

 principle, and consists of two tables, each capable of 

 being drawn longitudinally by a nui working on separate 

 screws, which screws can be geared to revolve at any 

 desired velocity. A plan of the ship is pinned on one 

 table and the rough model secured keel up on the 



lU 



-.Nail I'la: Physical l.ab.<r,it,.)ry I 



« .iter expi 



ductors supported along the west w.ill of the building; 

 these conductors are fed by a g( m rater, which again 

 is driven by a motor working on fifty-five cells. There 

 are complete arrangements for controlling the 

 voltage of the supply, so that the carrlai^c inav be 

 brought to any speed up to fifteen milis |>i r hour, and 

 the speed be kept constant over the main portion of 

 the run down the basin. This towing carriage will carry 

 a dynamometer and other recording instruments for 

 the measuring of the resistance, ^c, of the models. 

 These will be towed through the water in such a 

 manner that though free to trim or move fore and 

 aft to any extent necessary for equilibrium, no side 

 motion will be possible, special i^nidcs Ixing fixed 

 under the carriage to ensure thi>^. 



The models will be made of hard iiaraftin wax of 



NO. 2172, VOL. 86] 



centre line ol ilir srcond. ()\-fr iliis laiicr 

 are two nAoKin^ ciiidis l)i-iu('i-ii \\lii<h 

 passes. I'^u'li of thcsi' is diivcn In' a mi 

 motor altai'!i''(i (iiicrliv to llic u[)p(<r end of 

 Thev can be sn ai aii\ drsiicd liri^lil, and 



(1)\' IlUMIls 



i llllllati 



■ lateral motion o 



|)s in contact with 



verse motion bt mid^ i 

 gr.'ifih niorhanisni I, ili 

 uliirh the operator Ui 

 line on the plan cot re 

 cutters on the model. 

 this pantai.;rapli, and t 

 screws, any proportion 

 cut from fho ship's (liauin<^;. 



The modi] when ii comes from the 

 Upon it a series of hori.'ont.d cuid.nicc 

 v\a\ between which is trimmed off with 



londini^ lo ilie 

 l>\ adiusiin:: th 



• L^eariuL; lielwei 



>f Iciil;!!! and I'l 



tahle ihrro 

 the m<i(i<'l 



l.dj electric 

 its spindle. 



llteir tians- 



of a panta- 



f n ■ 



the 



i^hl o! ine 

 fulcrum of 

 the driving;- 

 (ilii can he 



^pokesh.ives 



