Step 1: Understanding the Concept:
In a potentiometer, the balancing length is directly proportional to the emf.
Step 2: Detailed Explanation:
$E_1 + E_2 = k \times 58$ and $E_1 - E_2 = k \times 29$. Dividing, $\frac{E_1 + E_2}{E_1 - E_2} = \frac{58}{29} = 2$. Solving gives $E_1 = 3E_2$, so ratio $E_1 : E_2 = 3:1$.
Step 3: Final Answer:
The ratio is 3:1.