We have measured the dissipation and frequency of nanocrystalline-diamond nanomechanical resonators with resonant frequencies between 13.7 MHz and 157.3 MHz, over a temperature range of 1.4 -274 K. Using both magnetomotive network analysis and a time-domain ring-down technique, we have found the dissipation in this material to have a temperature dependence roughly following T 0.2 , with Q Ϫ1 Ϸ10 Ϫ4 at low temperatures. The frequency dependence of a large dissipation feature at ϳ35-55 K is consistent with thermal activation over a 0.02 eV barrier with an attempt frequency of 10 GHz.

No abstract

a gentleman well known in his day both as a scientist and traveller. The major part of the collection unfortunately left this country, having been purchased by the dealer F. Krantz of Bonn. A few lots were, however, bought by myself, and one of these contained the first specimen to be here described.This specimen consists of one-half of a small geode 7 • 5 cm. formed of brown and velvety black limonite, some partially altered chalybite, ferruginous crystalline quartz, and a little galena. In this geode and upon the limonite are emplanted several very brilliant crystals of phosgenite, one large tabular crystal of anglesite, and numerous smaller crystals of laurionite. The specimen had no label, but besides being certainly Cornish, it came, almost without doubt, from the silver-lead mine of Wheal Rose in the parish of Sithney. With this specimen there were others of cerussite labelled Wheal 13o01 (a neighbouring mine). Further, the geode exactly resembles similar geodes containing cerussite and anglesite which have been found by myself on one of the old dumps at Wheal Rose. The limonite on all of the specimens is exceedingly characteristic of the locality, showing evidence of being pseudomorphous after chalybite.The other specimen, which is in the Brooke collection at Cambridge, (no. 2302) is especially referred to by Greg and Lettsom under cromfordite (phosgenite) as being the only specimen of that mineral known

WHEN red lead is submitted to the action of hot glacial acetic acid, a colourless solution is obtained which, on cooling, deposits crystals.