Professor Poopsnagle's Steam Zeppelin

Poopsnagle's grandson Peter also had an ancient parchment that his grandfather had left him, and on the parchment was a cryptogram written in Latin. After the cryptogram had been decoded, it was only a matter of time before they found the first golden salamander. The golden salamanders had been buried long ago to indicate where each mineral could be found. After the first one was found, the cryptogram on it would lead the children and the doctor to the next one. What they had to do in each case was to decipher the cryptogram on each salamander. The first one led them to a cave not far from Secret Valley, where after being caught in a mine shaft and surviving a gas explosion, they were able to find their way down the shaft and into an unknown valley where they found the second salamander and the first mineral.