Artillery - July 1st 1916 at 7.20am

[buritonian]

I’m very curious to understand the scene at 7.20am and 7.30am on July 1st on the Somme. In particular, where the 1st Hampshires jumped off. 
1) in that final hour before the off, what quantity and rate of shells were falling on the German lines in front of them? 
2) as the Hawthorn mine blew to their right did shelling stop altogether here as it lifted to hit other targets behind the enemy lines?

3) I also believe shells began to fall on their trenches as they waited for the whistles to blow. What volume/concentration of shells were falling. 
 

this has so far been a bit of a mystery to me, made less clear from what I see in Malins famous footage doesn’t show anything raining down in the moments before the mine blew.

if their are artillery tables or schedules that paint a picture it’d be great to know where to see them.

if anyone is able to describe the scene, in particular what German shells were hitting British trenches in those final minutes before the off I’d be grateful for the info.