$2 Scientifie Intelligence. (JAN. 
of basalt, porphyry, green-stone ; and veins of basalt having sides of 
pitch-stone traverse the sand-stone strata. These veins, it may be 
remarked, are of the same nature with those discovered in the 
island ef Lamlash, and agree with those discovered in Iceland 
by Sir George Mackenzie. 
III. Specific Gravity of Men. 
In the year 1757, Mr. Robertson published in the Philosophical 
Transactions a set of experiments on the specific gravity of men, 
He constructed a vessel, in which men might be immersed, and 
he determined the specific gravity by the rise of the water in the 
vesse]. Ten trials were made in this way onten labouring men 
belonging to the ordinary of Portsmouth yard. They were all 
thin, and varied in size from 6 feet 2 inches to 5 feet 34 inches. 
I am induced to republish the results here, because IJ see it in- 
serted in a contemporary Journal, that no experiments on this 
subject have ever been made. I have added a column exhibiting 
the specific gravity of the men, reckoning sea-water 1:000.  ~ 
, Specific Gravity. 
anne P arte =" 
Height. Weight. Rain water =1. Sea water = 1. 
Pe ciate apie, 2 ANCHOS ee LOLIDS. ie ok OUK Sin 9 gin nc eee 
Zc es er LOS ween we lS oe sige O'FUIG. e009 0 CONE 
SD ieee Dh Gls ane. naw OOo ares eo MOOD”, a pin oy Cie 
ME dela oe iY GS: | ote 'a'nlne LAC » oie sy ia OURa LA ants eae 
Livy) Caer as Dv Dice einige ie LPODHs 5 asig's OOS 4 yo: pain Ae 
Ghee Se OT De ors 2's 46 LOO wee te ZU OOOO ten + 5 Wee 
Pi ceilea's 5 Uh AES de wes Ai WED Vat sake aiel, CLE ttl am! Seem 
=e eA hers aft: eee aged fe ayn pil 0°8429 .... O°8195 
See role aS! Dar otal s ue My ra ara’ 5 on WCRI. i a 
TU coinealls spec in inte d'ahahsio a hes Lona din i or fiat isveretan Une 
From this table we see that all the men were lighter than sea- 
water, and that all, except one, were lighter than rain-water. 
The weight requisite to bring the lightest to the same specific gra- 
vity as rain-water would have been 28 lbs.; and to bring him to 
the specific gravity of sea-water very nearly 30 lbs would. have 
been required; while the heaviest man was only 0°6 of a lb, lighter 
than sea-water. 
IV. Criopyrite. 
(To Dr, Thomson.) * 
SiR, 
Jn consequence of some erroneous accounts which have made 
their way into the public papers, respecting a new engine of the 
power of twenty horses, said to be constructed under the direction 
of the inventor of the block machinery, it appears that the public, 
as well as your, Dundee correspondent, are very anxious to gain 
some more faithful account of this wonderful machine, for which a 
