(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 ofany 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.”