**The** **method** **gives** **directly**, **not** **k**, **but** **klc**. **P**. **G**.

**No** **calorimetric** **observations** **are** **required**, **but** **the** **results** **are** **obtained** **in** **terms** **of** **the** **thermal** **capacity** **of** **unit** **volume** **c**, **and** **the** **measurements** **give** **the** **diffusivity** **klc**, **instead** **of** **the** **calorimetric** **conductivity** **k**.

**We** **thus** **obtain** **the** **simple** **equation** **k**'(**de**'/**dx**') - **k**"(**de**"/**dx**") =**c** (**area** **between** **curves**)/(**T** - **T**'), (4) **by** **means** **of** **which** **the** **average** **value** **of** **the** **diffusivity** **klc** **can** **be** **found** **for** **any** **convenient** **interval** **of** **time**, **at** **different** **seasons** **of** **the** **year**, **in** **different** **states** **of** **the** **soil**.

**The** **presence** **of** **water** **in** **the** **soil** **always** **increased** **the** **value** **of** **klc**, **and** **as** **it** **necessarily** **increased** **c**, **the** **increase** **of** **k** **must** **have** **been** **greater** **than** **that** **of** **k**/**c**. 13.