Given that \( \log x = 0.25 \), we want to find \( \log x 4 \).
Using the power rule of logarithms, we have:
\[ \log x 4 = \log x (2^2) = 2 \log x 2 \]
Now we can express \( \log x 4 \) using the properties of logarithms. First, let's rewrite \( \log x 4 \):
\[ \log x 4 = \log (x^2) \]
Applying the power rule gives us:
\[ \log x 4 = 2 \cdot \log x \]
Now substituting \( \log x = 0.25 \):
\[ \log x 4 = 2 \cdot 0.25 = 0.5 \]
Thus, the value of \( \log x 4 \) is:
\[ \boxed{0.5} \]