We must thank Dr. Grzedzielski for the clarification of his argument and notation contained in his second note. Unfortunately, this note only shows more clearly the fundamental misconceptions and errors in his arguments. Our own argument as to the generality and validity of the initial strain concept remains unaffected.

In our previous note, we were concerned to explain the initial strain concept, which Dr. Grzedzielski had criticised as “ an oversimplification not generally admissible “ both in the calculation of thermal stresses and as a device to simulate the effects of structural cut-outs and modifications. Here, we prove independently by a direct consideration of the compatibility conditions in the final structure, that the modified stress distribution given by our analysis is the correct one—regardless of the extent of the coupling in the flexibility matrix.

It was nearly a year after the holding of the Aeronautical Exhibition, before the next meeting of the Society was held on 20th May 1869.

Despite the fact that in the first three years of the Society's life much attention had been paid to heavier-than-air ideas, the Chairman, Glaisher, had lost none of his enthusiasm for balloons for certain purposes.

“They met that night under peculiar circumstances,” he said, “there being in London at this time the largest balloon yet made.“

Glaisher referred to Henri Giffard's captive balloon, capable of lifting twenty people at a time. In a calm it could be held captive at 2,000 ft., and was exhibited at Ashburnham Park. Giffard placed the balloon at the disposal of Glaisher for taking meteorological observations, and he made close on 30 ascents in it on behalf of the British Association, in whose transactions the results are reported.