an early environmentalist, writing: "Up to our time, strict economy in the use of natural resources has not been practiced, but it must be henceforth unless we are immoral enough to impair conditions in which our children are to live," although he also believed the automobile would be a positive environmental factor, with the end of horse-based transportation bringing "a real step in civilization... With no smoke, no gases, no litter of horses, your air and streets will be clean and pure. This means, does it not, that the health and spirits of men will be better?" Like many men of his time, he also showed an interest in the supernatural, saying "If I were able to take the time, I believe that I could prove the continuation of life beyond the grave, reasoning from the necessity, philosophically speaking, of a belief in an absolute and universal power." Death When Burnham was in his fifties, his health began to decline. He developed colitis and in 1909 was diagnosed with diabetes, which affected his circulatory system and led to an infection in his foot which was to continue for the remainder of his life. On April 14, 1912, Burnham and his wife were aboard the RMS Olympic of the White Star Line, traveling to Europe to tour Heidelberg, Germany. When he attempted to send a telegram to his friend Frank Millet who was traveling the opposite direction, from Europe to the United States, on the RMS Titanic, he learned that the ship had sunk in an accident and Millet did not survive. Burnham died only 47 days later from colitis complicated by his diabetes and food poisoning from a meal eaten in Heidelberg. At the time of his death, D.H. Burnham and Co. was the world's largest architectural firm. Even legendary architect Frank Lloyd Wright, although strongly critical of Burnham's Beaux Arts European influences, still admired him as a man and eulogized him, saying: "[Burnham] made masterful use of the methods and men of his time...[As] an enthusiastic promoter of great construction enterprises...his powerful personality was supreme." The successor firm to Burnham's practice was Graham, Anderson, Probst & White, which continued in some form until 2006. Burnham was interred at Graceland Cemetery in Chicago. Memorials Tributes to Burnham include Burnham Park and Daniel Burnham Court in Chicago, Burnham Park in Baguio in the Philippines, Daniel Burnham Court in San Francisco (formerly