that the vertical lines of ships' masts be disrupted with irregular white bands. Hiding these would make ships less conspicuous, and would "greatly increase the difficulty of accurate range finding". However, in the same letter, Kerr also called for countershading, the use of paint to obliterate self-shading and thus to flatten out the appearance of solid, recognisable shapes. For example, he proposed painting ships' guns grey on top, grading to white below, so the guns would disappear against a grey background. Similarly, he advised painting shaded parts of the ship white, and brightly lit parts in grey, again with smooth grading between them, making shapes and structures invisible. Kerr was thus hoping to achieve both a measure of invisibility and a degree of confusion for the enemy using a rangefinder. Whether through this mixing of goals, or the Admiralty's skepticism about "any theory based upon the analogy of animals", the Admiralty claimed in July 1915 to have conducted "various trials" and decided to paint its ships in monotone grey, not adopting any of Kerr's suggestions. It had made up its mind, and all Kerr's subsequent letters achieved nothing. The American artist Abbott Handerson Thayer had developed a theory of camouflage based on countershading and disruptive coloration, which he had published in the controversial 1909 book Concealing-Coloration in the Animal Kingdom. Seeing the opportunity to put his theory into service, Thayer wrote to Churchill in February 1915, proposing to camouflage submarines by countershading them like fish such as mackerel, and advocating painting ships white to make them invisible. His ideas were considered by the Admiralty, but rejected along with Kerr's proposals as being "freak methods of painting ships ... of academic interest but not of practical advantage". The Admiralty noted that the required camouflage would vary depending on the light, the changing colours of sea and sky, the time of day, and the angle of the sun. Thayer made repeated and desperate efforts to persuade the authorities, and in November 1915 travelled to England where he gave demonstrations of his theory around the country. He had a warm welcome from Kerr in Glasgow, and was so enthused by this show of support that he avoided meeting the War Office, who he had been intending to win over, and instead sailed home, continuing to write ineffective letters to the British and American authorities. The marine artist and Royal Naval Volunteer Reserve officer