Click on the spiral tool in InkScape and draw a spiral. You can go to the top of the screen and choose the desired properties of your spiral, such as Turns, Divergence, and Inner Radius. Then select the spiral and make a copy of it. Rotate the copy by 180 degrees and position it within the the other spiral. Select the two spirals now by pressing Ctrl+A, then go to Path>>Object to Path. The last step is to connect the two objects. Click on the "Edit Paths by Nodes" tool and select the center node of one of the spirals. Then hold Shift and click on the centrer node of the other spiral. Click on the "Join Selected Nodes" button at the top of the screen. We want to do the same for the outer ends of the spirals. But because they are on opposite ends, we first have to delete some of the nodes on one spiral. Select the nodes that you want to delete, and click the "Delete Selected Nodes" button on the toolbar. Then, nome the nodes closer to one another and adjust the orientation handles on the nodes to get the position and orientation correct. Finally, select the two nodes that you wish to join by using Shift, and then click the "Join Selected Nodes" button as before.