Cut cucumbers and onions in 1/8 inch slices and place in separate bowls. Sprinkle 1/4 cup salt over cucumbers, 1 tbls over onions. Give both cucumbers and onions a good toss with a fork once during their 1 hour soaking period. Rinse in cold water and drain thoroughly. Make a syrup from the remaining ingredients. Stir to dissolve the sugar. Put drained cucumbers and onions in a large pot and pour the syrup over them. Cook over high heat to boling (about 10 minutes). Lift out cucumber and onion slices into sterilized jars. Cover with the hot syrup. Remove any surface bubbles and seal securely.