Don Bustamente 07i a new Gravimeter. 209 



same length as the instrument, and th^ diameter of which 

 is aHttle greater. In the interior of the bottom is firmly sol- 

 dered the conical end x z, in which is fitted a part of the cone 

 dec, and, as the diameter of the upper plate ought to be very 

 little less than that of the box, the instrument placed with- 

 in this cannot be shaken so as to spoil it ; and in this manner 

 it can be moved about with much convenience and security. 

 This box is also best for using the instrument, because a 

 sufficient quantity of water being put into it, and the instru- 

 ment being submerged, the water only reaches the brim with- 

 out spilling. 



6. When the instrument is left to itself in the water, it sinks 

 to very near the base a 6, as we have said, and it is necessary, 

 in order that the zero of the scale should reach the level of the 

 water, to put some little weights of lead in the upper plate ; 

 the weight of which ought to be ascertained, so that it may 

 always sink to that one point; and this new weight we will call 

 additional weight. 



7. If when in this state we put on the plate any weight, the 

 greater the weight the deeper it sinks ; and there is no doubt 

 that this new weight is equal to that of a cylinder of water 

 equal to the portion of tube that has been sunk, because the 

 space that this occupies in the liquid is equal to that occupied 

 by the cylinder of water which it dislodged, and the force of 

 the liquid to sustain it is also equal to that of the weight of 

 the substance, to be able to keep immersed that portion of the 

 tube. Thus, then, if the instrument sinks one of the divisions 

 of the scale, we can say that the weight with which it is char- 

 ged is equal to that of a cylindrical portion of water whose 

 base is the section of the tube, and whose height is one divi- 

 sion. A greater load will immerge it 20 divisions, and will be 

 equivalent to the weight of 20 portions equal to the preced- 

 ing. Knowing, then, the number of drachms or grains that 

 each of these portions weighs, we shall be able to ascertain the 

 weight of the substance that we put on the plate. 



8. Afterwards we will show how the weight of each portion 

 is known, although there is no necessity for its being known ; 

 because the divisions of the scale show us the correspondence 

 of the weights that we put on the plate, in the same manner 



VOL. X. NO. II. APRIL 1829- O 



