94 PHILOSOPHICAL TKANSACTIONS. [aNNO 1725. 



tilled oil of common thyme, by letting the oil stand at rest in the bottle into 

 which it had been received, a quantity of camphor, differing in no respects 

 from the genuine oriental camphor, except in its odour. This camphor had 

 shot into crystals of various sizes, some as large as filberts, and mostly of a 

 cubic form, like sugar candy, at the bottom of the bottle. This substance (he 

 observes) is very different from that obtained by Hoffman, (Dissert, de Camph. 

 ct Obs. Physico Chym.) from roses and the lignum aloes, as well as from that 

 which Mr. Boyle (Treatise on Solidity and Fluidity) obtained from the ol. anisi. 

 The product in these instances is merely unctuous, or at most only of the con- 

 sistence of butter, but not in the form of solid, friable crystals, as in the case 

 of the oil of thyme. — In the further part of this paper, the author shows that 

 camphor is a substance differing in its properties from oils, resins, volatile salts 

 and gums; that it is in fact a sui generis substance; and that it is ob- 

 tainable from thyme and perhaps from some other vegetables, besides the so 

 called camphor-tree. 



Observations of the Dipping Needle, made at London, in 1723. Bij Mr. 

 George Graham, F. R. S. N° 380, p. 332, 

 About the time Mr. G. was observing the variation of the horizontal needle, 

 he made also some experiments with the dipping needle, to try if the dip and 

 vibrations were constant and regular. The needle he made for this purpose, 

 was 12^ inches long, half an inch broad in the middle, but not above -j^ near 

 the ends; the ends themselves being filed to fine edges; and in thickness it 

 was about i of a tenth. The ends of the axis, on which the needle turned, 

 were very smooth, and not thicker than was necessary for the support of the 

 needle, which weighed Q''""' 21 grains, or about half an oz. Troy. The ends 

 of the axis were placed on the edges of two thin plates of steel, that were hard 

 and well polished, and parallel to the horizon, that the needle, when vibrating, 

 might roll, and not slide on the edges of the plates, to avoid the friction of 

 moving in holes. A brass semicircle was provided, and from the lowest point 



posthumous edition, which contains the whole of the author's lectures, consists of 3 vols. 4to. and 

 was printed at Ziiilichau 174-9. An English translation of his chemical works, abridged and metho- 

 dized by Lewis, was published first in 1 vol. 4to. 1760, and afterwards in 2 vols. 8vo. 1773. They 

 have also been translated into French and other Europsean languages. These lectures exhibit a better 

 view than had before been given by any other writer, of all that was then known in chemistry. They 

 moreover contain many new analyses made by the author himself of certain medicinal and alimen- 

 tary substances ; such as amber, opium, castor, tea, coffee, &c. It has been before stated in a note at 

 p. 55-i of the first vol. of these Abridgments, that he examined with much attention the acid juice 

 of ants, and showed (what has been confirmed by subsequent experiments) that it coincides in 

 its leading properties with the acetic acid. 



