PROVISIONAL REPORTS AND NOTICES. 209 



present meeting the report which has been just called for. Mr. Bache was re- 

 quested to prepare this report at the Meeting at Newcastle in 1838, which he 

 personally attended; it was also at that Meeting that the system originated of 

 combined magnetical and meteorological observations which is now in full and 

 successful action, and in which various governments and scientific individuals 

 of all nations participate. In our own and most other countries the expenses of 

 the establishments at which these observations are made have been defrayed 

 from national funds ; but in the United States this has not been done ; and 

 the task of procuring the necessary funds by private subscription for the 

 magnetic observatory at Philadelphia has been undertaken by Mr. Bache, in 

 addition to that of establishing it and superintending its progress. His exer- 

 tions in carrying into effect the wishes of the Association on this subject have 

 engrossed the time which he could otherwise have devoted to the preparation 

 of the report on the meteorology of the United States. We may, however, 

 expect that the report will be ready for a future meeting, and I need not say 

 to those who are acquainted with Mr. Bache's qualifications, that whenever 

 presented it cannot fail to form a very valuable contribution to our Transac- 

 tions." In reference to the progress and present state of the magnetic ob- 

 servatory at Philadelphia, Colonel Sabine read the following communication 

 from Mr. Bache. 



" Philadelphia, May 10, 1842. 



"My dear Colonel, — As I shall not have the advantage of joining the 

 magneticians in June, will you report to Section A. what we have been doing 

 here in concert with them ? The bi-hourly observations of declination and 

 horizontal and vertical force have been carried on regularly since their com- 

 mencement in June 1840, as well as the term-day observations. The me- 

 teorological instruments, including the barometer, the dry and wet bulb ther- 

 mometer, Daniell's hygrometer, the blackened bulb and radiation thermome- 

 ters, have also been observed at the intervals assigned in the general instruc- 

 tions. Osier's self-registering anemometer and rain-gauge have been kept 

 at work. Saussure's hair hygrometer has been observed for comparison. 

 The meteorological term-days have been kept as well as the magnetic, making 

 two during the month. These observations have been made with instruments 

 and in an observatory belonging to the Girard College of Philadelphia, and 

 have been kept up by voluntary contributions, chiefly from members of the 

 American Philosophical Society, and by funds furnished by the Society. 



" We have made some changes in the instruments which we consider im- 

 provements. Since January 1841 the vertical-force instrument has been 

 provided with a mirror, and is observed at a distance, like the declination and 

 horizontal-force instruments of Gauss. The only disadvantage which has 

 occurred in this is an increase in the correction for temperature, but the fa- 

 cility and certainty of the observations compensate for this. The arrange- 

 ment of the force part of the Anemometer ha3 been greatly improved by 

 connecting the plate which receives the action of the wind with slightly- 

 curved brass bars, or springs, placed at the side of the registering table ; 

 the action of the instrument is thus rendered much more regular. As we 

 have much snow in the course of a season, it was a problem of some inter- 

 est to measure its fall by the registering apparatus : this has been effected 

 by raising the temperature of the funnel of the gauge slightly above the 

 freezing point, by vapour from a boiler within the observatory. 



" During the first year the observatory was not heated artificially, but the 

 large and uncertain amount of the corrections for temperature induced me to 

 adopt a different course during the past winter, and without any of the bad 

 results which I had apprehended from currents of air. The instruments, 



1842. p 



