OF FORCE. 199 



stages of development, while cold and darkness arrest the same. It would seem that in color, 

 too, there resides a force more or less positive in its influence on development. Light trans- 

 mitted through colored glasses hastens development in some cases, but retards it in others : it 

 may not be fully determined, however, whether, in such arrangements, an injurious matter is 

 arrested by which the intensity of an active element is diminished, or whether it is the power 

 of color alone which deterrnines the result. There are facts which indicate that there is a force 

 in color, mdependent of other qualities of matter. The apparent force in color, it is true, may 

 be somewhat analogus to the power or force of quantity. It is well known to chemists that 

 quantity of matter is important in effecting changes in composition : in these cases it is not a 

 new force which operates, but the same force increased by usmg a larger quantity of matter. 

 We may, probably, secure important results in husbandry by availing ourselves of this law : 

 combinations may thereby be formed which are unknown without its aid. In plants disease 

 rarely, if ever, follows from a great supply of nutrient matter ; the assimilation in plants seems 

 to be equal, in all cases, to the task imposed. In animals there are limits to the power of as- 

 similation ; much may be done to favor the growth or increase, by judicious adjustments of 

 food to the condition and age of the animals. 



How is it that force is lost, in the process of time, by a growing body ? In annual plants it 

 would seem that the great effort and design of nature is the perfection of seed. To effect this, 

 the forces of the plant are, as it were, directed and concentrated to one point : when the seed 

 is perfected the work is done. But during this process many important changes have taken 

 place in the individual ; induration of the tissues or an impervious condition of the channels of 

 circulation have taken place, and the functions of the organs are impeded ; the incrusting mat- 

 ter of the cells, the essential organs of vitality, interrupt the free communication of the fluids 

 essential to growth. Considering these changes as due to chemical action, it is unphilosophical 

 to suppose that there is a loss of vital force. In the galvanic battery, the incrustation of the 

 plates diminishes the activity of the machine ; it is a mere mechanical obstacle, which being 

 removed and it works with the same force as when first put in operation. But in plants some 

 of the outward conditions are changed ; heat and external force has diminished with the pro- 

 gress of the season. More than one cause, therefore, exists for the apparent result that vitality 

 exhausts itself by its own action. 



The most curious exhibition of force is that which is furnished by presence, of Catalysis^ so 

 called by Berzexius. When the temperature of the common oil of vitriol is raised, and alcohol is 

 dropped into it, the oxide of ethyl and water are produced, which may be distilled off, without 

 diluting the acid. In this case the sulphuric acid remains unchanged, and does not combine 

 with the elements of alcohol ; but its presence decomposes the alcohol, and will continue to do 

 so for any period. There are many changes which may be classed under this head. Thus 

 the action of sulphuric acid on starch, by which the latter is changed into dextrine, is a very 

 remarkable example of catalysis, or the exhibition of a force by mere presence. Elements are 

 often active in the vegetable which chemists class under this head. Diastase, in its trans- 

 formation of sugar into carbonic acid or gum, is one equally familiar to the practical chemist ; 



