Copy letter from Robert William Frederick Harrison to W Gifford, Oaklands, Chard 'Dear Sir, In answer to your enquiry I beg to say that your joint paper on Vitreous Sillica is printed in Vol. 73 of the Proceedings [of the Royal Society], published in July 1904, and is to be found at p201 of that volume. The No. in which it appeared was No. 491, published in March 1904.' 16 November 1908