1826.] tlie Origin of Ergot. \t 



have fallen under my view, in relation to the cause of ergot; and 

 how far they go to support or oppose either of the theories here- 

 tofore adopted upon the subject, I submit to the decision of 

 others. 



In the conclusion of this article, perhaps it may not be impro- 

 per to state some facts in relation to the effect which the ergot 

 produces upon the health of the plant on which it grows. I was 

 never able to discover that the culm of rye was in the least 

 affected by the ergot ; but I have observed that invariably 

 where there were to the number of eight or ten grains of ergot, 

 no healthy or sound rye could be found in the same head. In 

 such cases it appears that all the nourishment which the culm 

 affords is exhausted by the ergot, and the rye sutlers a severe 

 blight. 



The size of the ergot is usually in proportion to the number of 

 grains in the same head. For when we find but one grain in a 

 rye-head, it is generally from 10 to 14 lines in length, and two 

 or three in diameter ; but where there are from 25 to 30 grains, 

 which is not unfrequent, their dimensions are proportionably 

 less, being often not greater than sound rye. 



Article III. 

 Analysis of ike Ore of Iridium. By T. Thomson, MD. FRS. 



In a paper inserted by Dr. Wollaston in the Philosophical 

 Transactions for 1805, he gives an account of an ore of iridium 

 which is intermixed with the grains of crude platinum, and which 

 remains unacted upon after the platinum has been dissolved in 

 nitro-muriatic acid. He picked out a number of these grains, 

 and gave an account of some of their most remarkable proper- 

 ties. They have a foliated texture, a peculiar lustre, are brittle, 

 and have a specific gravity of 19*5 ; thus constituting the 

 heaviest body hitherto discovered in nature. Dr. Wollaston 

 informs us that by analysis he could detect in it nothing but 

 iridium and osmium. He selected a portion of this ore, and 

 gave it to the late Mr, Smithson Tennant, requesting him to 

 make an exact analysis of it. 



Unfortunately this amiable and highly ingenious man was cut 

 off by a most melancholy accident before he had found leisure 

 to execute the projected analysis. I had received a quantity of 

 the same ore from Dr. Wollaston many years ago ; but as I 

 considered the investigation of the metals in crude platinum as 

 in some measure forbidden ground, I was unwilling to obtrude 

 upon it while there was any reason to expect that Dr. Wollaston 

 himself might be prevailed upon to undertake a task which he 

 was so mucli better qualified for th-^n any other person. But as 



New Series, vol. xi. c 



