_ A FORM OF FLYING-MACHINE. 49 
peer tore the siiieentin: Whointhee are plotted as in fig. I 
and resolved into thrust and useless work, which are plotted again. 
in the two curves of fig. II, the areas enclosed by the curves will 
represent ft. Ibs. for 4 of the first revolution of the crank-shaft 
from which is deduced the mean lbs. of thrust of both wings for 
the first revolution = 1-075 lbs., and mean lbs. of lost work of both 
wings for the first revolution = 2-26 lbs. Multiplying each of these 
quantities by 9 feet, the distamie traversed by the centre of effort 
of the wing gives 9-675 ft. lbs. of effective work and 20-34 ft. lbs. 
of lost work, the sum of which, 30-015 ft. lbs., is the work of the 
first stroke. 
machine during its flight is shown by fig. IV to be 41: 28 feet, 
multiplied by 1:47 Ibs. =60-68 ft. Ibs. ; but the whole work of the ~ 
first stroke is to the effective work of “the first stroke as the total 
work of the elastic bands is to the total thrust of the eight strokes, 
that is, as 30015 : 9-675 :: 168°8 : 54-4, giving a difference of ss 
6°28 ft. lbs., to which I attach little importance, as it may arise in ue 
a number of ways from the graphic method of investigation adopted. ee 
The centre of gravity of the machine when wound up is 2 feet 
es ; all measured from the forward end of the strut. 
Fig. VI refers to the strength of the tissue paper that is used. 
for the membrane of the planes ; it took over 28 lbs. to burst the 
tried, but it bellies, and is hard to stretch tightly. 
There have been so many breakages and ambiguous results due 
ait 
currents have no effect on the observations. The experiment 
described may be taken as considerably under what = twenty- 
four india-rubber bands wo o if the machine were more care- 
fully made ; and fig. V shows they can be stretched to 38 inches — 
with a strain of 20 Ibs., in this experiment they were only 
stretched to 303 inches, with 12°6 Ibs. ; but many of the india- 
rubber bands would not stand more than one or two of the long 
stretches, and accidents sey be frequent. 
_ It has occurred to me that the motion of this form of ae 
machine will produce sea-sickness, time will show if this is 
Mo. Bot. Garder 
1007... 
