(1) Because the volume of the gas in the bubble is constant, it changes with the same volume, and the pressure is proportional to the thermodynamic temperature, that is,

PT=△P△T=k (constant), and △P=△h, and △h is the change of mercury column height in the C tube.

△t=△T, so △t=k△h, which means that the temperature changes uniformly with height, so the scale of this thermometer is uniform;

(2) According to the gas equation Pt = p ′ t ′, there are:

76273=76+7.6273+t，

T=27.3℃

(3) When the atmospheric pressure increases to 78cmHg, the value measured according to the gas equation Pt = p ′ t ′ is greater than the real value.

If the temperature changes 1℃ on the scale, the actual temperature changes △ t ′ = 7678×1= 0.974℃.

So, the answer is: (1) even number; ? (2)27.3? (3) greater than 0.974