40 



Captain Kater's account of the 

 Bushel No. 4. 



In order to enable the reader to form some idea of the 

 errors of the measures of capacity, it may be remarked that 

 a drop of water is commonly estimated to be nearly equal to 

 one grain. 



As the quantity of water contained by the bushel measure 

 is determined by the surface of the glass plate, which should 

 be a perfect plane, a figure not easily attainable, it is not to 

 be understood that the capacity of the bushel is true within 

 the limits of the errors above-mentioned, but to the gallon, 

 quart, and pint measures, in consequence of their more ad- 

 vantageous form, this source of error does not in any sensible 

 degree apply. 



Verification of the standard yards with steel terminations. 



These standard yards were made by Mr. Dollond ; they 

 are of brass, one inch square. To their extremities are firmly 

 screwed rectangular pieces of steel of the same width as the 

 bar, and projecting above its surface. The distance between 

 the interior faces of the steel termination is intended to be 

 equal to the length of the imperial standard yard. 



