166 EIGHTH ANNUAL REPORT OF 



servations proposed in the preceding reports. Circulars describing the 

 plan of operation were distributed to the several parts of the Union 

 through members of Congress at the last session, and the results fully 

 equalled our anticipations. From localities widely separated from 

 each other, and distributed over the greater portion of the United States, 

 about one hundred and fifty monthly returns are now regularly re- 

 ceived. To carry on this system efficiently, much labor is necessarily 

 required in the way of correspondence ; but it bids fair to furnish the 

 Institution with a wide field of usefulness in bringing it into communi- 

 cation with individuals who, though secluded in position, are desirous 

 of improving themselves, as well as of promoting general knowledge. 

 The correspondence we have thus established, and which we hope to 

 extend, through the aid of the members of the present Congress, will 

 enable us to acquire definite information on a variety of subjects besides 

 those which relate to meteorology. We have already accumulated in 

 this way a mass of curious and instructive information, 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 by 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 atmospheric 

 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 from different positions 

 v ould 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 of 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, and 

 observed at suitable times and with undeviating regularity by competent 

 observers. Few persons are acquainted with the difficulty of procuring 

 accurate meteorological instruments. The ordinary thermometers for 

 sale in the shops frequently differ several degrees from each other, par- 

 ticularly at the higher and the lower temperatures, and even the same 

 thermometer is liable, for a time after its construction, to undergo a 



