I don't know why te button "fade" work and the button "slide" don't work ???

Any suggestion is welcome.

I put here the code also

HTML

2. <table>
3.     <tr>
4.         <td>a</td>
5.         <td>b</td>
6.         <td>c</td>
7.         <td>d</td>
8.      </tr>
9.      <tr id="divHidden" style="display: none; background-color:red;">
10.          <td colspan="4">
11.              <table>
12.                 <tr>
13.                     <td>e</td>
14.                     <td>f</td>
15.                     <td>g</td>
16.                     <td>h</td>
17.                  </tr>
18.              </table>
19.         </td>
20.      </tr>
21. </table>
22. <br><br><br>      
23.     <button id="fade" >Click me (fade) !</button>
24.     <button id="slide" >Click me (slide)!</button>
25. 
    

jQuery

2. $(document).on('click', '#fade', function(){
3. $('#divHidden').toggle("fade", 500);
4. });
5. 
   
6. $(document).on('click', '#slide', function(){
7.         $('#divHidden').toggle("slide", 500);
8. });
9. 
   

CSS

2. table, tr, td{
3.     border:1px solid black;
4. }
5. 
   

Thanks for the support

Bye