Jg ON PLATINA AND NATIVE PALLADIUM VROM BllASIL. 



pursuits, will think what has already been said fully suffi** 

 cient for his purpose. However, I will just mention that 

 there can be no danger, in the formation of this taVjle, of 

 taking from a wrong line the real errours which are to be 

 the criterion for finding that of the one under trial; because 

 they are in the next lint' to it; the others, which Intcivene 

 in the full table, not being yet inserted, The last course of 

 all is, however, an exception; forj as the examining micro- 

 scopes could not be brought near enough to bisect the an- 

 gle 2° 48' 45", recourse was had to that qiiantity and its 

 . • half; on which account the examination is prosecuted by 



iising errours at two lines distance, as is showu in the two 

 last exaui[)les. 

 All the com. When the table of real errours is constructed, the othe? 

 should be ore- t^^le, although it is of no farther use, should not be thrown 

 served. away; for, if any material mistake hys been committed, it 



w ill be discovered as the operation of dividing is carried on ; 

 and, in this jcase:>the table of apparent errours must be had 

 recourse to; indeed, not u figure should be deftroyed until 

 the work is done*. 



Respecting the angular value of the numbers in the?e ta- 

 bles, it may be worth mentioning, that it is not of the least 

 importance; 100 of them being comprised in one revolu- 

 tion of the micrometer screw ; and, in the instance before 

 lae, 5*6 of them made no more than a second. It is not 

 pretended, that one of these parts was seen beyond a doubt, 

 being scarcely t^Itttt of an inch, much less the tenths, as 

 (exhibited in the tables ; but, as they were visible upon the 

 raJcrometer heads, it was judged best to take them into the 

 account. 



/'To be concluded in our next.) 



II. 



On Wlatina and native Palladium from BrasU. By Wil- 

 liam Hyde Wollaston, M. D. Sec. R. Sf. 



Flatiri.i not jf\.LTHOUGH platina has now been known to mineralo- 

 found in Eu gists for more than s-ixty } ears, yet it had not been discover- 

 lope tUl lately, 



* This is a very useful hint, applicable on many ccciisions. C. 



t Fhiltis. Trans, for 1800, p. I89. 



