Calendar: 1972-1973 Page 459

Annual Report of the Delegacy lxxvii the University of London and the Mathematics Colloquium at the University of East Anglia He attended and lectured at the international conference on ring theory at Oberwolfach Germany at the conference on algebraic number theory at Oberwolfach and at the conference on rings and modules organised by the Hungarian Mathematical Society at Lake Balaton Hungary Professor Pirani gave an Open Lecture at Birmingham University on Science versus Social Responsibility and lectured at the Universities of Stockholm and Torun Professor Higgins was invited to address the British Mathe- matical Colloquium on 'Equational theories in universal algebra' Professor Higgins also lectured on 'Categories and set theory' at Leeds Aberystwyth and the University of Zambia and on 'Methods in combinatorial group theory' at Cardiff Professor Kilmister lectured to the British Society for Philo- sophy of Science on Constructivity and quantisation' and gave guest lecture at Chelsea College on 'The concept of stability with applica- tions' Dr Erdos lectured on 'Calculus in schools' at the University of Nottingham on 'Integral calculus' at the ILEA Mathematics Course for teachers on 'Lattices of invariant subspaces' at Imperial College and on Superdiagonalisation of compact operators' at Chelsea College Dr Robinson lectured on 'The energy of gravitational shock wave' to the Cambridge University Relativity Seminar and presented paper jointly with Dr Winicour on 'The possibility of negative gravitational energy' at the international conference on gravitation and relativity Copenhagen Dr Silvester lectured at the London University Algebra Collo- quium on On the K2 of free associative algebra and an extension of Nagao's Theorem' Dr Tyrrell lectured at the University of Nottingham Shell Centre on 'Vector spaces in Geometry' and at the London-Sussex Geometry Seminar on 'Rational normal quartics which touch four lines' The following people visited the department during the year Professor Stachel University of Boston all year Dr Mielnik Warsaw University one month Professor Ε Newman Pittsburg one month Professor White University of British Columbia Vancouver months Professor McCulloh University of Illinois all year Among many other visitors to the department during