To the Editor of the Scientific American Supplement:

Your issue of 17th October contains the fifth or sixth imprint of Mr. B. Baker's, C.E., recent address at the British Association of Aberdeen which has come into my hands.

In speaking of stone bridges, he alludes to the bridge over the Adda as 500 years old. It was never more than 39 years old as stated in the same address, and he belittles the American Cabin John Bridge by making its span "after all only 215 ft." As the builder of this greatest American stone arch, I regret that on so important and public an occasion the writer was not accurate.

The clear span of Cabin John Bridge is 220 ft. The difference is not great, but in the length of a bridge span it is the last foot that counts, as in an international yacht race to be beaten by one minute is to fail to capture the cup.

M.C. MEIGS.

Washington, D.C., Oct. 16, 1885.