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thev ^row. We expect tcio much, and that too soon, from our 

 few experhnents in the cultivation of economic science. Such 

 expectations are apt to end in the putting foward of ill consider- 

 ed theories and hasty suggestions, alike dishonorable to science 

 and injurious to the popular verdict upon its worth. 



By a publication made in h^ngland while this address was in 

 preparation, I can illustrate this branch of my subject by a note- 

 worthy instance of a most delicate and abstruse method of research 

 in Botany yielding the practical results which have long been 

 sought for in the agriculture of two continents. The microscope in 

 its most modern and powerful form, is now in constant use for 

 the minute examination of the invisible structure of animals and 

 plants. Many things which live, and are powerful by their num- 

 bers, are individually only to be recognized or described under 

 the lens. Their germs, which are smaller still, contain in their 

 structure and development the secret of their bane or blessing 

 to the world. It is a chamber most obscure and far removed 

 from practical life, as your first thought might say, which is here 

 unlocked by the optician's art. \'et the microscope has just 

 achieved an honorable fame from the value of one of its revela- 

 tions. 



The potato murrain, as English authors call it, has for some 

 time been a most dreaded pest in Europe and America. Dark 

 spots upon the leaves, foliage and stems blackening and decay- 

 ing, the tuber corrupted by the same hidden cause and dissolv- 

 ing in a fetid slime, these are the well known symtoms of the 

 disease. The evil has been found to be a delicate white mould — 

 whose threads mine and exhaust the plant. Such moulds are 

 among the worst precursors of pestilence or famine. They are 

 more fearful than the devouring fire, They belong to a class of 

 l^lants called Eungi, jjarasitic destroyers all, the scavengers of 

 the vegetable world. It is such a mould as you may see in Au- 

 tumn, at once the murderer and shroud of the flies dead upon 



