Harlan, soldering wire connections was a common and good practice back in the day. That was mostly due to the fact that wirenuts hadn't been developed yet. You can still solder these conections but it is alot of unnescesary work on your part and if you have to work on that connection again in the future say to change a device for another you will hav to unsolder them or cut of the solder "bug". I have had to do this in my old house restore and it left me with very little wire left to work with. My advice is to mack it easy on yourself and use wirenuts and tape them over.