(2) Show that Mill’s methods may properly be termed “Inductive Methods of Scientific Investigation.” (3) How may it be shown by “agreement” that the high cost of living is due to the tendency to spend more than we earn? (4) Assume that you are a member of the Board of Health, and that you desire to ascertain the cause of the diphtheria epidemic by means of the principle of agreement. (5) What is the error involved in coming to the conclusion that to sit at table where there are thirteen, may mean the death of _one_ of the thirteen before the end of the year. (6) Indicate how it could be shown, by the method of difference, that the mosquito is responsible for the propagation of yellow fever. (7) “Another experiment similar to this was tried by Plateau, who put some food of which cockroaches are fond on a table and surrounded it with a low circular wall of cardboard. He then put some cockroaches on the table; they evidently scented the food, and made straight for it. He then removed their antennae.” (Hibben). Complete and give with explanations the method used. (8) “In some cases it is impossible to remove an element which is supposed to be the cause of an effect under investigation.” Explain and illustrate. (9) “Extreme care must be taken that, in the withdrawing of any element, no other element is inadvertently introduced.” Tyndale supposed he had proved _spontaneous generation_, when, after sealing in a jar of boiled water a wisp of baked hay, he found, after many days, indications of life within the bottle. In transferring the hay to the bottle, he carried the former across the room. What element was inadvertently introduced? (10) “The attempt to determine the numerical relations according to which two phenomena vary, requires the utmost caution as soon as our inference outsteps the limits of our observations.” (Fowler). Explain this in connection with the law of concomitant variations. (11) “When the effects of all known causes are estimated with exactness and subducted, the _residual facts_ are constantly appearing in the form of phenomena altogether new, and leading to the most important conclusions.” Make clear by illustration this quotation which has reference to the principle of residues. (12) Explain “invariable conjunction of phenomena.” (13) Investigate by means of one of the five methods the following problems: (1) “All vegetables which grow to root should be planted during the last two days of the waxing moon.” (2) “In this section the _south_ wind is the _storm_ wind.” (3) “Mischief is the outcome of misdirected energy.” (4) “Bad boys usually receive unjust treatment.” (5) “An ounce of prevention is worth a pound of cure.” CHAPTER 19.