234 PROCEEDINGS OF THE CALIFORNIA 



ally with regard to the authorities. He had not been able to meet 

 him, but would nevertheless lay the results of his researches before 

 them. The circulation in the polar basin was indicated by the 

 position of the ingress and egress of warm waters, and their vol- 

 umes ; by the observations of explorers ; by the position and species 

 of drift-wood ; and by the limits of animal life and human habita- 

 tions. Authorities were brought forward to illustrate and sustain 

 his previous positions, and especially to disprove the existence of a 

 Wrangell continent, by the deposits of wood on the western shores 

 of Bank's Land and Prince Patrick Island ; " There was far more 

 drift-wood on the north-west coast of Prince Patrick Island than 

 anywhere else on the polar coasts of the entire Parry archipelago." 

 These deposits had been particularly denied by M. Pavy. The 

 route to the pole from the Siberian region was not new, but first 

 proposed in 1810. 



An analogy was drawn between the polar regions of Mars and 

 those of the Earth, to show the persistence of ice and snow at the 

 poles. 



Prof. Davidson explained the method which he had adopted, 

 whilst making experiments for the Government at the U. S. Branch 

 Mint at San Francisco, for determining the difference of two weights 

 of supposed equal weight, by the system of " cross-weighing"; and 

 by the same operation determining the statical moment of the arms 

 of the beam. The statical moment, he designated as the length- 

 weight of the arms, with their adjuncts of pans, etc. 



The variable flexure of a beam renders untrustworthy any ex- 

 periments by cross-weighing ; but the method is available where 

 the beam is rigid, and not hable to irregular derangements. As is 

 well known, the method of cross-weighing consists in placing two 

 supposed equal weights in the pans of an adjusted beam, and estab- 

 lishing their equilibrium by adding fractional weights to the appar- 

 ently lighter one. The weights are then interchanged, and the 

 beam again brought into equilibrium, as before. The diiference of 

 the two weights was then assumed approximately, from the relation 

 of the additional fractions to either pan. 



Prof. Davidson solved the conditions algebraically, and gave the 

 following example of the method ; wherein L represents the column 

 of observations noted in the left pan, and R, those of the right 



