I do exactly the same thing. Although, I have found that the elevations on Jeffrey's Map and the elevations on Google Earth do not always match. It may depend on how accurate you are with your cursor and how far you have "zoomed in". So, take it with a grain of salt.
Just to clarify for people who have not used the Google Earth path feature. Create a path on Google Earth by choosing the ruler icon and then selecting the path tab in the ruler window. Now create the path by drawing lines on the map with your mouse. Once you have created a path you have to save it before you can see the paths elevation profile. Once saved hover your mouse over your path. Press the right button and then choose View Elevation Profile. Tadaa!
Another neat feature, if you hover your mouse cursor anywhere over the elavation profile window a little arrow will show where you are on the path. You can hold down the left button on your mouse as you drag the curser across the elevation profile. This will show the elevation gain/loss and average slope of that section of your path. Very handy for judging a Portage.
Complete Canadian Toporama Maps for Google Earth can be found here: http://www.gelib.com/natural-resources- ... porama.htm
Click on the Blue button "Download with Google Earth". You can use these maps in the same way you use Jeffreys's Map. However this KMZ file just points to the data on the Government servers. It does not provide the maps themselves as a huge download. You must have an internet connection to view these Toporama maps in Google Earth.