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The experiments made with the Whirling Machine give the 
resistances which bodies whirled round in the air experience 
to considerable nicety, and have been considered as correctly 
giving the resistance which the same bodies respectively would 
have experienced if they had moved in straight lines. In this 
paper it was shewn that the centrifugal force communicated to 
the air, as is continually seen in various winnowing machines 
and blowing machines, required consideration, and that the ex- 
periments must be separated from those in which bodies move 
nearly in a straight line through the air. 
(3) On the comparison of the results given by the for- 
mula for the resistances which bodies experience 
whilst moving through fluids, investigated im the 
paper read before the Society on 7th March, 1870, 
with the experimental results found by Mr Robins 
and Dr FHutton by means of the Ballistic Pendu- 
lum. By R. Porrer, M.A, 
In this paper computations from the mathematical formule 
obtained in a paper read before the Society on 7th March, 1870, 
were compared with the results found experimentally by Mr 
Robins and Dr Hutton with the Ballistic Pendulum, to deter- 
mine the resistance which musket and cannon shot experienced 
on passing through the air. It was shewn that the computed 
and experimental results agreed as closely as could be expected 
in such a subject, and that we may now maintain that the 
refractory problem of resistances to motion in the air has at 
length been solved mathematically. 
Mr GLAISHER mentioned some observations in which he had 
been engaged, which shewed that the formula for resistance 
p=tkv’ did not hold in several cases, especially where p was 
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