Frazer,] ^Oi [March 2, 



A. Cross section of bad White Oak X 135. 



B. " " good " " X 135. 



C. " " t'arya porcina X 112, grouping of ducts and pushing 



aside of Medullary rays. 



D. Fragment of MedulUxrj' ray showing the pits or pores in the walls, X 300. 



An improvement in the construction of the Hypsometrical Aneroid. By Dr. 

 Persifor Frazer. 



(Read before the American Philosophical Society, March 2, 1883.) 



While in France last year the idea occurred to the writer to lessen the 

 weight of the delicate Hicks Barometer by constructing as much as possi- 

 ble of it of aluminium. Supposing that this could be done without 

 difficulty, though of course at an increased expense, the writer devised a 

 case of cork to contain it, and wrote to Mr. Hicks of London asking him 

 to make the attempt. After a number of interviews it was finally estimated 

 that the cost of the new form of aneroid should not exceed £10, or just 

 double that of the ordinary instrument of brass in a wooden case. Delays 

 were experienced from the beginning and added very much to the expense 

 of the instruments when they finally arrived here. 



First it was found difficult to produce an aluminium dial plate with a 

 graduation of the requisite delicacy and accuracy. Then the internal 

 supports could not be easily cast in that metal of the shapes necessary to 

 build the frame for the more delicate moving parts. 



Finally the writer was obliged to leave England without having received 

 the barometers. When they arrived a few days ago the Government duty 

 on them was §30.40 a piece, added to which Mr. Hicks had found it neces- 

 sary to increase the original charge of £10 to £15 apiece. In consequence 

 they cost a little over $105 apiece. 



They are, however, creditable to Mr. Hicks's workmanship, and if their 

 manufacture should increase, could no doubt be obtained at a very much 

 reduced price.* 



In order to prevent the breaking of the cork, by friction on the clothing, 

 a light canvas cover was added, weighing 50 grams. 



The following is a comparison of the weights of the ordinary Hicks 

 barometer with one of them. 



Old form. New form. 



Case and strap, 400 grams, (wood) 150 grams, (cork) 



Aneroid, 1000 " (brass) 400 " (Aluminium) 



Canvas cover, 50 " 



Total weight, 1400 " 600 



or 3.09 Its. (av.) 1.323 lbs. (av.) 



The ordinary instrument weighs, therefore, 2^- times as much as the new 

 form, the Aveight of the old case being closely that of the new barometer. 



*A letter received from IMr. Hicks, after the al)Ove was in print, reiterates 

 the difticulties with which he contended, and states that notwithstanding the 

 experience gained in making uiinu, lie cannot deliver them lor less than ilS 

 apiece. 



