286 ANNUAL OF SCIENTIFIC DISCOVERY. 



sulphate of lime is formed, and appears as a precipitate, whilst 

 the hydrated chloride of aluminium remains dissolved. On allow- 

 ing the aqueous solution to evaporate at a very gentle heat, and 

 afterwards cooling, crystals of hydrated chloride are produced. 

 If an attempt be made to drive off the water from hydrated chlo- 

 ride by the application of heat, decomposition will take place. 

 Hydrochloric acid is evolved under these conditions, and oxy- 

 chloride of aluminium is formed, and, by pushing the process, 

 alumina is obtained as the ultimate fixed product. The Lancet. 



A NEW SFHYGMOSCOPE. 



In the " Centralblatt " of the 25th of June, M. Landois gives an 

 account of a new sphygmoscope, which so far differs in construc- 

 tion from those that have been hitherto suggested that the move- 

 ments of the pulse act on a column of gas, the undulations of 

 which can be recognized by the movements of the flame resulting 

 from the ignition of the gas as it issues. M. Landois observes 

 that the iiacure of the dichrotic curve or secondary elevation in 

 the pulse, so commonly depicted, has not as yet been satisfac- 

 torily determined ; some believing it to be a real undulation, 

 others that it is to a certain extent an artificial curve, and due to 

 a kind of recoil of the instrument. None of the tracings obtained 

 by the various forms of instruments hitherto suggested are free 

 from this peculiar undulation, whether we take the mercurial col- 

 umn, as in the instrument of Chelins ; the column of water, as in 

 that of Naumann ; the elevation of a lever, as in that of Veerordt ; 

 or, lastly, a spring, as in that of Marey. The instrument sug- 

 gested by M. Landois appears to be a small metal chamber, the 

 edges of which fit closely on the wrist or elsewhere, whilst a 

 small space is left between the skin and the inside of the chamber, 

 through which either ordinary gas or hydrogen is transmitted 

 from a gasometer at a very low pressure. The gas issues by a 

 capillary glass tube attached to the other extremity of the cham- 

 ber, and can easily be ignited. It is interesting to find that the 

 movements thus rendered visible agree precisely, both as regards 

 the principal curve and the secondary undulation, with those ex- 

 hibited by means of Marcy's sphygmograph. The Lancet. 



THE VALUE OF AMERICAN HEMP IN MEDICINE. 



Dr. H. C. Wood, Jr., has written an essay, which he read before 

 the American Philosophical Society, in which he records some 

 experiments with an article of hemp grown in Kentucky. He 

 took an alcoholic extract made from the dried leaves, swallowing 

 at a dose nearly all the product of an ounce and a half of the 

 leaves, with the effect of profound hemp intoxication. It proved 

 to be toxic in its power, although he recovered himself in a day 

 or two. He had all the exuberant hilarity usually experienced 

 from the hemp, followed by a feeling of fear of impending death ; 



