Febbuaey 22, 1907] 



SCIENCE 



315 



account of its peculiar properties, which ren- 

 dered its isolation and investigation a matter 

 of extreme difficulty. 



Sodium azoimide, NaN^, when treated with 

 dimethyl sulphate, yields methylazide. 



N 



and this, by the action of methylmagnesium 

 iodide (Grignard's reagent) and water gives 

 diazoaminomethane, which is a colorless 

 liquid, melting at —12°. It is extremely 

 reactive and is decomposed during the course 

 of its preparation by the catalytic action of 

 the small quantity of impurity usually present 

 in magnesiimi. It boils at 92°, but promptly 

 decomposes, volatilizes readily at the ordinary 

 temperature, more rapidly at the boiling point 

 of ether and is miscible in all proportions with 

 every solvent. Acids convert it instantly into 

 nitrogen, methylamine and the methyl ester 

 of the acid. In dilute solution it has a sweet 

 taste, but the pure compound rapidly cauter- 

 izes and blisters the skin, and its vapor, when 

 inhaled, produces severe headache accom- 

 panied by a prolonged feeling of lassitude. 

 Diazoaminomethane forms a silver salt, 

 CHjN:]SI'N(Ag)CH3, and a cuprous salt, 

 CH.N:NN(Cu)CH3, the latter crystallizing 

 in large, lustrous, yellow prisms. It is by 

 means of this compound that the separation 

 and final purification of the diazoaminome- 

 thane was effected. 



J. Bishop Tinglk 

 Johns Hopkins Univebsitt 



CURRENT NOTES ON METEOBOLOOY 

 MOISTURE FROM CLOUDS 



Some interesting observations have lately 

 been made by Marloth on the amount of 

 moisture deposited by the S. E. trade clouds 

 on vegetation growing on the summit of Table 

 Mountain, South Africa (Trans. So. Afr. 

 Phil. Soc, XIV., Pt. 4, Oct., 1903; XVI., Pt. 

 2, Oct., 1905; Met. Zeitschr., Dec, 1906). In 

 this southwestern extremity of South Africa 

 the winter is rainy and the summer dry. 

 About three quarters of the annual precipita- 

 tion falls in the six winter months, and in the 



three summer months (Dec.-Feb.) only about 

 eight per cent., 2.16 dnches, falls on the 

 average. It occasionally happens that two 

 months may pass without a drop of rain. The 

 vegetation on the hills and on the lower slopes 

 of the mountains clearly reflects the deficiency 

 of summer precipitation, but on the moun- 

 tains vegetation is much more abundant, and 

 shows much more favorable conditions of 

 moisture supply. The latter has been shown 

 by Marloth to come from the clouds formed 

 over the mountains in the S. E. trade wind. 

 The plants collect the cloud drops in suf- 

 ficient quantity, not only to keep themselves 

 wet, but even to furnish enough water to 

 produce a permanent swamp on the top of 

 Table Mountain in winter, and a periodic 

 swamp in summer. The summer swamp dries 

 up during long spells of clear weather, but 

 appears again when the S. E. cloud is formed. 

 Small ponds actually form, sometimes even 

 in late summer, on the top of Table Moun- 

 tain. A photograph of a pond appears in 

 Marloth's report. An interesting piece of evi- 

 dence as to the effect of the water thus col- 

 lected by vegetation is given in the note that 

 in the case of a mountain stream in this 

 region, which can furnish sixty horse-power, 

 three days after a fire which burned off the 

 bushes and grass at the head of this stream, 

 the water furnished only twenty horse-power. 

 The cloud on Table Mountain is a mixture of 

 an ordinary cloud and very finely distributed 

 rain-drops in process of formation. The 

 whole mass moves at high velocity (the trade 

 velocity is there often forty miles an hour), 

 which prevents the fall of small drops. It is 

 not until they come in contact with a solid 

 object, and when the velocity is reduced, that 

 the drops are held by the obstacle, and gradu- 

 ally reach the ground. 



In connection with this phenomenon refer- 

 ence may be made to various suggestions that 

 have been brought forward regarding the pos- 

 sible utilization of fog for the uses of vegeta- 

 tion in California {Mo. Wea. Rev., Oct., 1898, 

 466 ; 1899, 301, 473) ; also to Hann's ' Hand- 

 book of Climatology' (English translation), 

 195-196. 



