On a rainy Monday afternoon, Sherlock Holmes gets a call from a wealthy banker to arrange a breakfast appointment for the following day to discuss the collection of a loan from farmer Joe. When Holmes arrives at the home of the banker at 9 a.m. Tuesday, he finds the body of the banker in his kitchen. The farmer’s house is located on the other side of a lake, approximately 10 km from the banker’s home. Since there is no convenient road between the home of the farmer and that of the banker, Holmes phones the police to question the farmer. The police arrive at the farmer’s home within the hour and interrogate him about the death of the banker. The farmer claims to have been home all night. The tires on his truck were dry and he explains that his boots were moist and soiled because he had been fishing at the lake early in the morning. The police then phone Holmes to eliminate farmer Joe as a murder suspect because he could not have been at the banker’s home since Holmes spoke to him. Holmes then calls the local weather bureau and learns that, although the temperature had been between 2°C and 5°C for weeks, it had dropped to –30°C quite suddenly on Monday night. Remembering that a 3 cm layer of ice can support a man, Holmes takes out his slide rule and heat transfer text, lights his pipe, makes a few calculations, and then phones the police to arrest farmer Joe. Why?
GIVEN
Murder suspect with flakey alibi