464 Scientific Intelligence. [June, 



we have had during the winter ; but the weather afterwards 

 became more settled, and the barometer attained its maximum 

 of elevation. It will be seen that the spaces described and the 

 number of changes exactly correspond with those for January ; 

 but the mean is less than for many years past. 



April. — Mean pressure of barometer, 29-581 ; max. 30*49 ; 

 min. 28-89 ; range, 1-60; spaces described, 7*08 inches; number 

 of changes, 14. Mean temperature, 42-96°; max. 60° ; min. 29°; 

 ranee, 31. Amount of rain and snow, 3-98 inches. Wet 

 days, 6 ; snowy, 4 ; total quantity of rain, &c. this year, 15'56 

 inches. Prevailing winds, N. E. and N.E. ; N.5 ; N.E. 9; E. 6; 

 S.E. 1 ; S. 4 ; S.W. 4 ; Var. 1. Brisk winds, 5. Character of 

 the period : cold, wet, and changeable, and unfavourable to 

 vegetation. On the 10th and 24th the violence of the snow 

 storms was nearly unparallelled ; and on the moors and wolds it 

 lay in drifts several yards thick, and did considerable damage. 

 From 10 p. m. (26th) to two p. m. (27th), we had a heavy fall of 

 rain, attended with incessant, vivid red lightning and loud thun- 

 der all the time. The next day another thunder storm passed 

 here to the S. and S.W. where it was visible from six to 

 eight p. m. 



When the above periods are compared with those for the last 

 year, either as to the pressure, temperature, or to any other 

 feature, there is no similarity whatever. The first four months 

 last year were fair, dense, and mild ; but those now elapsed have 

 presented characters decidedly the reverse. The amount of rain 

 and snow from January 1 to May 1, in 1817, did not exceed 3^- 

 inches ; and there were only 34 wet days ; but the quantity of 

 rain this year amounts to 15i inches, and there has been rain or 

 snow in a greater or less decree on 76 days out of the 120. 



NewMalton, May 4, 1818. 



o. 



IT. Analysis of a Specimen of the Diamond Rock. 



Dr. E. D. Clarke, Professor of Mineralogy at Cambridge, has 

 examined a specimen of the diamond rock, from the banks of the 

 river ligitonhonha, in Brazil, which was sent to him for this 

 purpose by Mr. Mawe, of the Strand. It contains diamonds in 

 their matrices. The rock consists of an aggregate of small 

 quartz pebbles firmly set in indurated iron sand. The cavities 

 in which the diamonds are placed are invested by a yellow 

 ochreous matter which is full of minute pallets of native gold, 

 visible to the naked eye. 



From the same Professor we have also received an answer to 

 the queries of our Lewes correspondent. The metallic lustre 

 with which pure silica becomes invested when fused before the 

 gas blow-pipe, is sometimes due to the charcoal used as a 

 support ; the same appearance takes place, under similar circum- 

 stances, in the fusion of corundum, and other refractory bodies, 

 such as mamesia, and lime. But Dr. Clarke has observed 

 6 4 



