13 [120] 



thus established, and which we hope to extend, throngli the aid of the 

 members of the present Congress, will enable us to acquire definite inform- 

 ation on a variety of subjects besides those which relate to meteorology. 

 We have already accumulated in this way a mass of curious and in- 

 structive information relative to various subjects, which we hope, in the 

 progress of the development of the plan of the institution, to digest and 

 present to the public. 



We would mention in this connexion that two of our meteorological 

 correspondents have proposed the collection of statistics of diseases, in- 

 cluding the rise, progress, and decline of epidemics. This is a subject 

 we would commend to the American Medical Association. The Smith- 

 sonian Institution could assist in an enterprise of this kind l)y receiving 

 the information which is attainable, and collating it, under the direction 

 of a committee of gentlemen belonging to the medical profession. 



It will be recollected that our plan of meteorological observations em- 

 braces three classes of observers — one to record the changes in the aspect 

 of the sky, the direction of the wind, beginning and ending of rain, 

 snow, &c.; another, in addition, to give an account of the changes of 

 temperature indicated by the thermometer; and a third, furnished with a 

 full set of instruments for recording the most important atmosplieric 

 changes. The importance of the information which may be derived from 

 a careful record of the weather without instruments can scarcely be 

 realized by persons who have given but little attention to the subject. 

 The place of origin, direction, velocity of motion of a storm, as well as 

 the direction and velocity of the wind which composes it, whether gyra- 

 tory or inward and upward, may all be determined by a sufficient amount 

 of data of the kind we have mentioned. Also, a careful record of the 

 observations of meteors seen by individuals fromditl'erent positions would 

 furnish interesting data for determining the elevation and velocity of 

 these mysterious visitors. 



There are other data which can only be obtained by the use ol accu- 

 rate instruments: fortunately, however, a comparatively small number 

 of observers are sufficient for'determining these. The instruments should 

 be of the best possible construction , placed in important situations, observed 

 at suitable times and with undeviating regularity by competent observers. 

 Few persons are acquainted with the difficulty of procuring accurate me- 

 teorological instruments. The ordinary thermometers for sale in he 

 shops frequently differ several degrees from each other, particularly at the 

 higher and the lower temperatures, and even the same therniometer is 

 liable, for a time after its construction, to undergo a change in the size of 

 the bulb, and thus to derange the accuracy of the scale An accura e 

 bai-ometer is another instrument which cannot readily be obtained, unless 

 at too great a price for the means of ordinary observers. The common 

 weathefglasses^old under the name of barometers, ^1-"? Yhu7a"sL't in 

 of use in indicating variations of atmospheric pressure, and thus assist n 

 tnSrIng dlta for^deternnaing the progress of ^^^^^J^^^^^ 

 cable to the precise and accurate observations ^^^^^^f^^ ^ ^^^^^^^^^^^ 

 minute changes of atmospheric pressure, or of asceitaining the liei^Ut ol 



places above the level of the sea. , ascertain 



^ Considerable pains have been taken d^^g the Past >^7^^^^^^^^^^^ 

 the best form of a barometer, which could be procured at a rea^onable 



