30 THE VICTORIAN NATURALIST. 



Tlie sediments from red niiii were collected at St. Kilda 

 14th February and 28th March, 1903, and at Camberwell 14th 

 February, 1903. 



Samples collected at St. Kilda, 14/2/03 : — 



No. I. — Obtained at 4.30 ]).m., rain having been falling 

 over 20 minutes. Lower atmosphere clear, with low drifting 

 clouds. Wind about due west, and blowing strongly. 



No. 2. — Collected at 6.30 p.m. \ 



No. 3 ,, at 7.30 p.m. ^Conditions as above. 



No. 4 ,, at 7.45 p.m. ) 



No. 5. — Collected at 8.30 p.m. Rain falling steadily. A 

 further sample obtained after 9 p.m. contained no appreciable 

 sediment. 



Sample collected 28th March, St. Kilda (one only), treated 

 for Diatomace?e. 



Sample collected at Camberwell, between 6.15 p.m. and 

 7.15 p.m., examined especially for minerals, but diatoms as 

 numerous as at St. Kihla. 



With respect to the series of sediments obtained on 14th 

 February, those collected between 4.30 p.m. and 6.30 p.m. were 

 found to contain the largest proportion of mineral and organic 

 material, and do not differ appreciably from a sample secured on 

 28th March under almost precisely similar conditions. This 

 latter sample was preferably treated for Diatomace^e alone, as the 

 total amount of sediment was somewhat greater than that collected 

 on the first-named date. As the February samples were 

 obtained at definite intervals they afford a comparison both as to 

 the amount and nature of the sediments. They also point to a 

 gradual diminution in the size of the contained particles. This is 

 first noticeable in the 7.45 sample, while that obtained at 8.30 

 p.m. is almost entirely free from the coarse grains characteristic 

 of the earlier gatherings. Most of the sediment collected 

 from 8.30 p.m. on to past 9 p.m. was so fine as to remain in 

 suspension for some hours. From this it would appear that the 

 heavier particles are carried down during, say, the first two hours' 

 rain. After this, assuming a continuation of similar conditions, 

 the amount of sediment is greatly reduced, and consists only of 

 particles in a minute state of subdivision. 



Minerals in the MELrsouRNE City Dust from the Roof 

 OF the National Museum. 



Quartz. — Numerous sub-angular chips. 



Orthoclase rare ; frequently schillerizetl ; one minute crystal 

 showing twinning on the Carlsbad ty[)e. 



Sanidine variety rare, in clear fragments ; one specimen with 

 characteristic cleavage cracks. 



