Letter from Herbert F Angus, H F Angus and Company, 83 Wigmore Street, Cavendish Square, London, to William Fletcher Barrett, St Stephen's Green East, Dublin He has read Barrett's pamphlets with interest and has duplicated the experiments. Discusses the three items of apparatus referred to: the entoptiscope; the optometer; and the light threshold and colour-blindness apparatus. He cannot advise that Barrett should put them on the market, but would be happy to retain one of them as a demonstration model and this might generate orders. 8 April 1909