METEOROLOGICAL REGISTER. 



Preliminary Explanatioiis . 



The observations on the modifications of the clouds were particu- 

 larly detailed in the Journal by Mr. Say, who bein<; often remote from 

 the party on detached expeditions, the phases observed by him cannot 

 always be considered as precisely corresponding with those that oc- 

 curred where the observations noted in the remaining columns of the 

 tables were made by Lieut. Grah;un. As they would occupy too much 

 space, if introduced into the body of this work agreeably to the ma- 

 nuscript notes, it was judged proper to modify and condense them 

 into the smallest possible space. With this view, the nomenclature 

 of Messrs. Howard and Forster has been adopted, and is now inserted 

 in the meteorological tables, under the indications of the following 

 abbreviations, viz. 



S - Stratus. 



C - Cirrus. 



Cs - Cirrostratus — the addition of a full point, thus Cs. 



shows that this cloud was almost or entirely 

 universal; and a comma, tluis, Cs, indicates its 

 partial occurrence. The same observations also 

 relate to the signs for the following clouds. 

 Cm - Cumulus. 

 Cml - Cirrocumulus. 

 Cms - Cumulostratus. 

 Cmc - Cumulocirrostratus. 

 Ns - Nimbus. 



But as the particular varieties of appearance which these respective 

 clouds exhibited, could not be indicated in the allotted columns of the 

 tables, they are altogether omitted. The column headed with the 

 word courses indicates the points of the heavens from which the clouds 

 proceed; thus | C. | S.W. | shows the occurrence of the Cirrus form 

 of clouds proceeding from the south-west. 



The letter L. sometimes inserted in the column of remarks on the 

 state of the weather, indicates lightning; 'l\ ihtnider, and R. rain. 



Observations, by means of the Cyanoineter, on the colour of the 

 atmosphere, were also made, three times each day, by Mr. Graham; 

 but as the instrument became imperfect in consequence of the fading 

 of its colours, from the necessary exposure to the action of light, they 

 have been rejected. 



No record was made of the liumidity of the atmosphere, as the Hygro- 

 meter provided for the use of the Expedition, proved entirely useless. 

 Simultaneous meteorological observations were made at German- 

 town, near Philadelphia, by Mr. Reuben Haines; from which the ave- 

 rage temperature of that place during- several months has been deduced 

 and inserted for the sake of compaiison, in the following tables. 



Observations on the state of the weather were regularly made 

 during the whole term of the expedition, but being too voluminous to 

 be inserted in the work, it was thought best to select those of an entire 

 year and reject the remainder. 



