44 Experiments on the Adhesion of Iron Spikes, &c. 
TABLE Iv. 
_ Spikes dr driven to different depths. 
Gicay 2at re a rae F TS le 6 (as 
se é Se gi (Fuses (. (8 a 
a a a3 Blo IS-aole-n 18918 sioe 
3 oy og n Sears kolenls 
sé : 33 S18 JF eslog |S5)[ESe 
el ud CG put ~~ yy | 
= & = eS = lg. Zio O-s|_B S5/5 3|Sz 
es 8 Se S fealesslse KolSaloml g 
M nl =I oO psajyo So fore omnes. ~ 
a eS |ee 82185 Fee BF) 4 
& = il ia 7D ics ; 
chesnut un- | sqoin. jinches.| grs. | 1835. 
1 feagerenst et seasoned. | .405) 402) .7695| 1.9 | 483/1183 2.428) Dec. 4. 
2 «} © 11.1745] 2.9 | 789 1995)2.528) 
axe tS ir | 11.5795! 3.9. |1095)2565/2.342|..* 
4 Broad fat. : .539, 288] 9702) 1.8 | 449/1595/3.457) 
5 * «| |15092) 2.8 | 745)2594'3.482' 
By comparing experiments I and 4 together, it will be found that 
weight f for Lee the flat spike had when driven 1.8 inches, an ad- 
vantage of 42.3 per cent. over the square one; and by a like com- 
parison of experiments 2 and 5; it is evident the former had a supe- 
riority of 37.7 per cent. “As the spike when driven in only 1.9 
inches had a much less proportion of its parallel faces exposed to 
the reaction of the fibres and a greater proportion of the wedge- 
shaped point, it is reasonable to expect that the retention would not 
correspond precisely with the lengths inserted. It will be understood 
that when we speak of cutting edges and the wedge-shaped portion 
of spikes, whether square, flat, or cylindrical, the direction of the 
cutting edges is always across the fibre or grain of the timber. It 
must be evident that the wedge-shaped part may be so acute, as to 
correspond nearly with two parallel faces, in which case, the tenden- 
cy to retreat from the lateral pressures is small; and the pressures 
themselves, increasing from the point upwards to where the spike is 
thickest, the total efficiency of a given length may be as great as that 
of an equal length of the parallel faces, and even greater, provided 
the thickness of the spike be so considerable as in driving it to pro- 
duce much crushing and irregular folding of the fibres of the timber. 
If, on the other hand, the edge be very blunt, the tendency to recoil 
may be such as to diminish the adhesion, and in this case the effect 
vo the wedge shape is me ingest In the other it way be positive.* 
= _The following storms may represent the several 
i aml free; in 
hi is the observed retention; l= the length in pre of the part inserted ; 
Fcsiee of retention on one tock of the parallel faces, andc¢= the difference 
‘the retention of a parallel portion of the spike, and of an equal length of 
Soe faces near the point. The sign of ambiguity arises from the cause 
ve 
