EEPOET OF THE SECEETAEY. 27 



The expedition, during which these observations were made, was 

 organized and principally equipped through the enterprise of Dr. 

 Hayes, assisted by contributions of a number of liberal gentlemen 

 interested in the advance of physical geography. The principal ob- 

 ject of the enterprise was the extension of the explorations of Dr. 

 E. K. Kane north of Baffin's Bay, and to make such observations as 

 would add to our knowledge of the physical condition of the arctic 

 regions. The expedition was mainly furnished with instruments by 

 the Coast Survey and the Smithsonian Institution, and after its re- 

 turn the records of its observations in their rough state, or as they 

 were made, were presented to the Institution for reduction and dis- 

 cussion. 



It is scarcely necessary to mention that scientific truths are not 

 generally immediately deduced from the simple observation of phenom- 

 ena, but that these require in most cases corrections to free them 

 from the effects of extraneous and other causes. Thus in observing 

 the place of the moon or a planet, the position as given directly by 

 the instrument must be corrected for refraction, for parallax and 

 for instrumental errors. So with the observations of the baro- 

 meter, a correction must lie applied for the relative expansion of the 

 mercury and of the brass case in which the glass tube is contained, 

 and also for capillarity, and in many cases for the elevation of the 

 instrument above the level of the sea. 



After the observations have been submitted to the process of 

 correction, to which the name of reduction has been applied, they are 

 then in a condition for scientific analysis, or for what is technically 

 called discussion. It seldom happens that any phenomenon is the 

 result of a single approximate cause. In almost all cases the effect 

 observed is the result of a series of concurring causes, and it is the 

 object of the scientific inquirer, if possible, to ascertain the separate 

 effect of each. For example, the height of the tide at a given place 

 and time is due to the conjoint action of the sun and moon modified 

 by the form and direction of the coast, to concurring or adverse tidal 

 waves, and also to the direction of the wind. In a successful discus- 

 sion each of these effects should be separately exhibited, and the 

 amount of the several influences of each critically ascertained. With- 

 out such reduction and discussion the crude observations exhibit a 

 mass of figures without apparent connexion, and give no indication 

 of the relation of phenomena. Unfortunately the labor attending 

 these processes is so great, and in many cases the skill required so 

 unusual, that individual enterprise and ordinary attainment are in- 



