Referee's report by Frederick Alexander Lindemann, on a paper 'The modes in which valency is exercised. Part II - The tetrahedral carbon atom' by Henry Edward Armstrong Sectional committee: Chemistry Not recommended for publication. Understanding the constitution of diamond and graphite is hardly needed since X-ray technology has been introduced. The thermo-dynamic relations have already been worked out. [Not published]. Endorsed on verso as received 29 June 1928. June 1928